diff --git a/.travis.yml b/.travis.yml
index bde2ff9554..0f81d9fcb7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -21,12 +21,6 @@ install:
 script:
   - npm test
 
-before_deploy:
-  - npm run clean
-  - npm run build
-  - npm run bundle
-  - npm run minify
-
 deploy:
   provider: npm
   email: remi@cliqz.com
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 69c3995fc4..3f80760cae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,18 @@
 # Adblocker
 
+## Next
+
+*not released*
+
+  * Add hard-coded circumvention logic (+ IL defuser) [#59](https://github.com/cliqz-oss/adblocker/pull/59)
+    - Simplify 'example' extension
+    - Add circumvention module and entry-point in cosmetics injection
+    - Clean-up cjs and esm bundles
+    - Remove obsolete logic to override user-agent in content-script
+    - Simplify travis config (using new pre* hooks)
+    - Consolidate 'fetch' module (with metadata about lists)
+
+
 ## 0.3.0
 
 *2018-11-20*
diff --git a/example/Makefile b/example/Makefile
index 9f9a5a469d..e81984d736 100644
--- a/example/Makefile
+++ b/example/Makefile
@@ -1,22 +1,13 @@
 
-.PHONY: content-script.bunble.js background.bundle.js build/example watch clean
+.PHONY: all watch
 
-ROLLUP="../node_modules/.bin/rollup"
-
-all: content-script.bundle.js background.bundle.js
-
-build/example:
-	tsc -p tsconfig.json --module ES6 --outDir build
-
-content-script.bundle.js: build/example
-	${ROLLUP} -c rollup.content.js
-
-background.bundle.js: build/example
-	${ROLLUP} -c rollup.background.js
+all:
+	npx tsc -p .
+	npx rollup -c rollup.config.js
 
 watch:
-	concurrently 'tsc -p tsconfig.json --module ES6 --outDir build --watch' 'rollup -c rollup.content.js --watch' 'rollup -c rollup.background.js --watch'
+	npx concurrently 'tsc -p . --watch' 'rollup -c rollup.config.js --watch'
 
 clean:
-	rm -frv *.bundle.js
+	rm -frv *.iife.js
 	rm -frv build/
diff --git a/example/README.md b/example/README.md
index ee7fa7b05b..402ede7d74 100644
--- a/example/README.md
+++ b/example/README.md
@@ -1,10 +1,12 @@
 # Minimal Content Blocker
 
-This is a minimal webextension doing adblocking/antitracking using most popular
-block-lists. It is meant as a very thin wrapper around the [adblocker](https://github.com/cliqz-oss/adblocker)
-library.
+This is a minimal webextension doing adblocking/antitracking using most
+popular block-lists. It is meant as a very thin wrapper around the
+[adblocker](https://github.com/cliqz-oss/adblocker) library. You can use it to
+debut the adblocker, or test new features.
 
-## Building
+## Workflow
 
-1. Build the extension: `make all`
-2. Load it in Firefox or Chromium by using the "Load unpacked extension" feature
+1. `make watch` will build and monitor for changes
+2. Open your browser and load "unpacked extension" from the `example` folder
+3. On re-build, reload the extension in browser
diff --git a/example/background.ts b/example/background.ts
index f50dea9e97..4f8d5ce46b 100644
--- a/example/background.ts
+++ b/example/background.ts
@@ -28,7 +28,7 @@ function loadAdblocker() {
       }
 
       engine.onUpdateResource([{ filters: resources, checksum: '' }]);
-      engine.onUpdateFilters(lists, new Set());
+      engine.onUpdateFilters(lists, new Set(), true);
 
       return engine;
     },
@@ -68,12 +68,14 @@ chrome.tabs.onCreated.addListener((tab) => {
 });
 
 chrome.tabs.onUpdated.addListener((_0, _1, tab) => {
-  if (tabs.has(tab.id)) {
-    const { source } = tabs.get(tab.id);
-    if (source !== tab.url) {
-      resetState(tab.id, tab.url);
-      updateBadgeCount(tab.id);
-    }
+  if (!tabs.has(tab.id)) {
+    resetState(tab.id, tab.url);
+    updateBadgeCount(tab.id);
+  }
+  const { source } = tabs.get(tab.id);
+  if (source !== tab.url) {
+    resetState(tab.id, tab.url);
+    updateBadgeCount(tab.id);
   }
 });
 
diff --git a/example/content-script.ts b/example/content-script.ts
index 530ad3b018..14202bec57 100644
--- a/example/content-script.ts
+++ b/example/content-script.ts
@@ -17,15 +17,18 @@ import { CosmeticsInjection } from '../index-cosmetics';
  */
 const backgroundAction = (action, ...args): Promise<void> => {
   return new Promise((resolve) => {
-    chrome.runtime.sendMessage({
-      action,
-      args,
-    }, (response) => {
-      if (response !== undefined) {
-        injection.handleResponseFromBackground(response);
-      }
-      resolve();
-    });
+    chrome.runtime.sendMessage(
+      {
+        action,
+        args,
+      },
+      (response) => {
+        if (response !== undefined) {
+          injection.handleResponseFromBackground(response);
+        }
+        resolve();
+      },
+    );
   });
 };
 
@@ -39,10 +42,9 @@ const backgroundAction = (action, ...args): Promise<void> => {
  * - Observe mutations in the page (using MutationObserver) and inject relevant
  * filters for new nodes of the DOM.
  */
-const injection = new CosmeticsInjection(
-  window,
-  backgroundAction,
-);
+const injection = new CosmeticsInjection(window, backgroundAction);
+
+injection.injectCircumvention();
 
 /**
  * Make sure we clean-up all resources and event listeners when this content
diff --git a/example/manifest.json b/example/manifest.json
index 2618eb2904..1b600dd725 100644
--- a/example/manifest.json
+++ b/example/manifest.json
@@ -16,7 +16,7 @@
   ],
   "background": {
     "scripts": [
-      "background.bundle.js"
+      "background.iife.js"
     ]
   },
   "browser_action": {
@@ -27,7 +27,7 @@
       "match_about_blank": true,
       "all_frames": true,
       "js": [
-        "content-script.bundle.js"
+        "content-script.iife.js"
       ],
       "matches": [
         "http://*/*",
diff --git a/example/rollup.background.js b/example/rollup.background.js
deleted file mode 100644
index 45ec265b9d..0000000000
--- a/example/rollup.background.js
+++ /dev/null
@@ -1,10 +0,0 @@
-import configs from '../rollup.config.js';
-
-export default {
-  input: './build/example/background.js',
-  output: {
-    file: 'background.bundle.js',
-    format: 'iife',
-  },
-  plugins: configs[0].plugins,
-};
diff --git a/example/rollup.config.js b/example/rollup.config.js
new file mode 100644
index 0000000000..e275fd1203
--- /dev/null
+++ b/example/rollup.config.js
@@ -0,0 +1,27 @@
+import resolve from 'rollup-plugin-node-resolve';
+import commonjs from 'rollup-plugin-commonjs';
+
+
+const plugins = [
+  resolve(),
+  commonjs(),
+];
+
+export default [
+  {
+    input: './build/example/background.js',
+    output: {
+      file: 'background.iife.js',
+      format: 'iife',
+    },
+    plugins,
+  },
+  {
+    input: './build/example/content-script.js',
+    output: {
+      file: 'content-script.iife.js',
+      format: 'iife',
+    },
+    plugins,
+  },
+];
diff --git a/example/rollup.content.js b/example/rollup.content.js
deleted file mode 100644
index 8249baadbb..0000000000
--- a/example/rollup.content.js
+++ /dev/null
@@ -1,11 +0,0 @@
-import configs from '../rollup.config.js';
-
-
-export default {
-  input: './build/example/content-script.js',
-  output: {
-    file: 'content-script.bundle.js',
-    format: 'iife',
-  },
-  plugins: configs[0].plugins,
-};
diff --git a/example/tsconfig.json b/example/tsconfig.json
index 05cb4c0e16..8c0ee2ebda 100644
--- a/example/tsconfig.json
+++ b/example/tsconfig.json
@@ -1,6 +1,7 @@
 {
   "extends": "../tsconfig.json",
   "compilerOptions": {
+    "outDir": "build",
     "noImplicitAny": false
   },
   "files": [
diff --git a/index-cosmetics.ts b/index-cosmetics.ts
index a7b31d3162..c30b742aaf 100644
--- a/index-cosmetics.ts
+++ b/index-cosmetics.ts
@@ -1,2 +1 @@
 export { default as CosmeticsInjection } from './src/cosmetics-injection';
-export { overrideUserAgent } from './src/cosmetics-injection';
diff --git a/index.ts b/index.ts
index 7d6c26a4e4..6a78d0600f 100644
--- a/index.ts
+++ b/index.ts
@@ -1,6 +1,5 @@
 // Cosmetic injection
 export { default as CosmeticsInjection } from './src/cosmetics-injection';
-export { overrideUserAgent } from './src/cosmetics-injection';
 
 // Blocking
 export { default as FiltersEngine } from './src/engine/engine';
@@ -8,8 +7,8 @@ export { default as ReverseIndex } from './src/engine/reverse-index';
 export { default as Request } from './src/request';
 export { deserializeEngine } from './src/serialization';
 
-export {default as matchCosmeticFilter } from './src/matching/cosmetics';
-export {default as matchNetworkFilter } from './src/matching/network';
+export { default as matchCosmeticFilter } from './src/matching/cosmetics';
+export { default as matchNetworkFilter } from './src/matching/network';
 
 export { parseCosmeticFilter } from './src/parsing/cosmetic-filter';
 export { parseNetworkFilter } from './src/parsing/network-filter';
diff --git a/package-lock.json b/package-lock.json
index 3198821cf9..42b1f17bcf 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2028,6 +2028,12 @@
       "integrity": "sha1-De4/7TH81GlhjOc0IJn8GvoL2xM=",
       "dev": true
     },
+    "estree-walker": {
+      "version": "0.5.2",
+      "resolved": "https://registry.npmjs.org/estree-walker/-/estree-walker-0.5.2.tgz",
+      "integrity": "sha512-XpCnW/AE10ws/kDAs37cngSkvgIR8aN3G0MS85m7dUpuK2EREo9VJ00uvw6Dg/hXEpfsE1I1TvJOJr+Z+TL+ig==",
+      "dev": true
+    },
     "esutils": {
       "version": "2.0.2",
       "resolved": "https://registry.npmjs.org/esutils/-/esutils-2.0.2.tgz",
@@ -4647,6 +4653,15 @@
         "yallist": "^2.1.2"
       }
     },
+    "magic-string": {
+      "version": "0.25.1",
+      "resolved": "https://registry.npmjs.org/magic-string/-/magic-string-0.25.1.tgz",
+      "integrity": "sha512-sCuTz6pYom8Rlt4ISPFn6wuFodbKMIHUMv4Qko9P17dpxb7s52KJTmRuZZqHdGmLCK9AOcDare039nRIcfdkEg==",
+      "dev": true,
+      "requires": {
+        "sourcemap-codec": "^1.4.1"
+      }
+    },
     "make-error": {
       "version": "1.3.5",
       "resolved": "https://registry.npmjs.org/make-error/-/make-error-1.3.5.tgz",
@@ -5752,6 +5767,18 @@
         "@types/node": "*"
       }
     },
+    "rollup-plugin-commonjs": {
+      "version": "9.2.0",
+      "resolved": "https://registry.npmjs.org/rollup-plugin-commonjs/-/rollup-plugin-commonjs-9.2.0.tgz",
+      "integrity": "sha512-0RM5U4Vd6iHjL6rLvr3lKBwnPsaVml+qxOGaaNUWN1lSq6S33KhITOfHmvxV3z2vy9Mk4t0g4rNlVaJJsNQPWA==",
+      "dev": true,
+      "requires": {
+        "estree-walker": "^0.5.2",
+        "magic-string": "^0.25.1",
+        "resolve": "^1.8.1",
+        "rollup-pluginutils": "^2.3.3"
+      }
+    },
     "rollup-plugin-node-resolve": {
       "version": "3.4.0",
       "resolved": "https://registry.npmjs.org/rollup-plugin-node-resolve/-/rollup-plugin-node-resolve-3.4.0.tgz",
@@ -5771,6 +5798,16 @@
         }
       }
     },
+    "rollup-pluginutils": {
+      "version": "2.3.3",
+      "resolved": "https://registry.npmjs.org/rollup-pluginutils/-/rollup-pluginutils-2.3.3.tgz",
+      "integrity": "sha512-2XZwja7b6P5q4RZ5FhyX1+f46xi1Z3qBKigLRZ6VTZjwbN0K1IFGMlwm06Uu0Emcre2Z63l77nq/pzn+KxIEoA==",
+      "dev": true,
+      "requires": {
+        "estree-walker": "^0.5.2",
+        "micromatch": "^2.3.11"
+      }
+    },
     "rsvp": {
       "version": "3.6.2",
       "resolved": "https://registry.npmjs.org/rsvp/-/rsvp-3.6.2.tgz",
@@ -6376,6 +6413,12 @@
       "integrity": "sha1-PpNdfd1zYxuXZZlW1VEo6HtQhKM=",
       "dev": true
     },
+    "sourcemap-codec": {
+      "version": "1.4.4",
+      "resolved": "https://registry.npmjs.org/sourcemap-codec/-/sourcemap-codec-1.4.4.tgz",
+      "integrity": "sha512-CYAPYdBu34781kLHkaW3m6b/uUSyMOC2R61gcYMWooeuaGtjof86ZA/8T+qVPPt7np1085CR9hmMGrySwEc8Xg==",
+      "dev": true
+    },
     "spawn-command": {
       "version": "0.0.2-1",
       "resolved": "https://registry.npmjs.org/spawn-command/-/spawn-command-0.0.2-1.tgz",
diff --git a/package.json b/package.json
index 942b0ce0c2..5afd53fae2 100644
--- a/package.json
+++ b/package.json
@@ -8,9 +8,9 @@
   },
   "author": "Cliqz",
   "license": "MPL-2.0",
-  "main": "dist/cjs/index.js",
-  "module": "dist/es6/index.js",
-  "jsnext:main": "dist/es6/index.js",
+  "browser": "dist/adblocker.umd.js",
+  "main": "dist/adblocker.cjs.js",
+  "module": "dist/adblocker.esm.js",
   "types": "dist/types/index.d.ts",
   "files": [
     "dist",
@@ -20,11 +20,13 @@
   "scripts": {
     "clean": "rm -rfv dist",
     "lint": "tslint -c tslint.json 'src/**/*.ts'",
-    "build-es6": "tsc -p tsconfig.json --module ES6 --outDir dist/es6",
-    "build-cjs": "tsc -p tsconfig.json --module commonjs --outDir dist/cjs",
-    "build": "npm run build-es6 && npm run build-cjs",
+    "build": "tsc -p tsconfig.json",
     "bundle": "rollup -c rollup.config.js",
-    "minify": "google-closure-compiler --js=./dist/adblocker.umd.js --js_output_file=./dist/adblocker.umd.min.js",
+    "minify": "google-closure-compiler --js=./dist/adblocker.umd.js --js_output_file=./dist/adblocker.umd.min.js && google-closure-compiler --js=./dist/adblocker-cosmetics.umd.js --js_output_file=./dist/adblocker-cosmetics.umd.min.js",
+    "prebuild": "npm run clean",
+    "prebundle": "npm run build",
+    "preminify": "npm run bundle",
+    "prepack": "npm run minify",
     "pretest": "npm run lint",
     "test": "jest --coverage --no-cache ./test/",
     "dev": "jest --watch ./test/"
@@ -47,6 +49,7 @@
     "jest": "^23.6.0",
     "jsdom": "^11.12.0",
     "rollup": "^0.67.0",
+    "rollup-plugin-commonjs": "^9.2.0",
     "rollup-plugin-node-resolve": "^3.4.0",
     "ts-jest": "^23.10.4",
     "tslint": "^5.11.0",
diff --git a/rollup.config.js b/rollup.config.js
index c3d0072ac6..44877e9cea 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -1,18 +1,16 @@
 import resolve from 'rollup-plugin-node-resolve';
+import commonjs from 'rollup-plugin-commonjs';
+import pkg from './package.json';
 
 const plugins = [
-  resolve({
-    module: true,
-    jsnext: true,
-    main: false,
-    preferBuiltins: false,
-    modulesOnly: true,
-  }),
+  resolve(),
+  commonjs(),
 ];
 
 export default [
+  // Custom bundle for content-script, contains only a small subset
   {
-    input: './dist/es6/index-cosmetics.js',
+    input: './build/index-cosmetics.js',
     output: {
       file: './dist/adblocker-cosmetics.umd.js',
       name: 'adblocker',
@@ -20,13 +18,23 @@ export default [
     },
     plugins,
   },
+  // Browser-friendly bundle
   {
-    input: './dist/es6/index.js',
+    input: './build/index.js',
     output: {
-      file: './dist/adblocker.umd.js',
+      file: pkg.browser,
       name: 'adblocker',
       format: 'umd',
     },
     plugins,
   },
+  // Commonjs and ES module bundles (without third-party deps)
+  {
+    input: './build/index.js',
+    external: ['tldts', 'tslib'],
+    output: [
+      { file: pkg.module, format: 'es' },
+      { file: pkg.main, format: 'cjs' },
+    ],
+  },
 ];
diff --git a/src/content/circumvention.ts b/src/content/circumvention.ts
new file mode 100644
index 0000000000..7e1075b869
--- /dev/null
+++ b/src/content/circumvention.ts
@@ -0,0 +1,13 @@
+import instart from './circumvention/instart';
+
+/**
+ * This module exports a single function which will be called from content
+ * script to inject some circumvention logic without having to perform a
+ * round-trip to the background. This is required for some websites where
+ * circumvention is done from the main document and counter-measures need to
+ * take effect immediately.
+ */
+export default (window: Window): void => {
+  // Custom logic to defuse InstartLogic
+  instart(window);
+};
diff --git a/src/content/circumvention/generic.ts b/src/content/circumvention/generic.ts
new file mode 100644
index 0000000000..e987d8df2d
--- /dev/null
+++ b/src/content/circumvention/generic.ts
@@ -0,0 +1,55 @@
+import { bundle } from '../injection';
+
+/**
+ * This module exports scriptlets building blocks which can be injected in
+ * pages. Each scriptlet is a function which can accept some arguments as well
+ * as a list of dependencies (functions which need to be available in the scope
+ * whenever the script runs in the page).
+ */
+
+/**
+ * Intercept and ignore errors originating from one of our scripts (if it
+ * contains the `magic` string which is unique to each content-script)
+ */
+export const swallowOwnErrors = bundle((magic) => {
+  // Keep track of original `onerror` callback, if any
+  const windowOnError = window.onerror;
+
+  // Wrap `onerror` into our custom handler to intercept our own exceptions
+  const customOnError = function(this: Window, msg: any) {
+    if (typeof msg === 'string' && msg.indexOf(magic) !== -1) {
+      return true; // do not fire default event handler
+    }
+
+    if (windowOnError instanceof Function) {
+      return windowOnError.apply(this, arguments);
+    }
+
+    return false;
+  }.bind(window);
+
+  Object.defineProperty(window, 'onerror', {
+    get: () => customOnError,
+    set: () => {
+      /* Cannot override */
+    },
+  });
+});
+
+export const protectConsole = bundle(() => {
+  const originalConsole = window.console;
+  const originalLog = console.log;
+
+  Object.defineProperty(console, 'log', {
+    value: function fakeLog() {
+      for (let i = 0; i < arguments.length; i++) {
+        if (arguments[i] instanceof HTMLElement) {
+          return;
+        }
+      }
+      return originalLog.apply(originalConsole, arguments);
+    }.bind(console),
+  });
+
+  Object.defineProperty(console.log, 'name', { value: 'log' });
+});
diff --git a/src/content/circumvention/instart.ts b/src/content/circumvention/instart.ts
new file mode 100644
index 0000000000..05b5ec13b2
--- /dev/null
+++ b/src/content/circumvention/instart.ts
@@ -0,0 +1,426 @@
+import { getWindowHostname, magic as contentScriptMagic } from '../helpers';
+import { bundle } from '../injection';
+import { swallowOwnErrors } from './generic';
+
+/**
+ * This module contains custom logic to defuse InstartLogic. It was heavily
+ * inspired by work done by uBlockOrigin's and AdGuard's developers.
+ */
+
+function isCurrentScriptInstart(thisScript: HTMLScriptElement | SVGScriptElement | null): boolean {
+  const script = document.currentScript;
+
+  if (script === thisScript) {
+    return false;
+  }
+
+  if (script instanceof HTMLScriptElement) {
+    const src = script.src;
+    if (src.indexOf('instart.js') !== -1 || src.indexOf('?:i10c.') !== -1) {
+      return true;
+    }
+
+    const scriptContent: string | null = script.textContent;
+    if (
+      scriptContent !== null &&
+      (scriptContent.indexOf(':Instart-') !== -1 ||
+        scriptContent.indexOf('I10C') !== -1 ||
+        scriptContent.indexOf('IXC') !== -1 ||
+        scriptContent.indexOf('INSTART') !== -1)
+    ) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+/**
+ * Protect a few global objects from being accessed or set by a script from IL.
+ */
+const shieldPropertiesFromInstart = bundle(
+  (magic) => {
+    const thisScript = document.currentScript;
+    [
+      'atob',
+      'console.error',
+      'INSTART_TARGET_NAME',
+      'navigator.userAgent',
+      'performance',
+      'require',
+    ].forEach((target: string) => {
+      // Handle nested targets
+      let obj: any = window;
+      const chain = target.split('.');
+      const prop = chain.pop();
+      chain.forEach((part: string) => {
+        obj = obj[part];
+      });
+
+      if (prop === undefined || obj === undefined) {
+        return;
+      }
+
+      // Protect obj[prop] by preventing access to InstartLogic
+      Object.defineProperty(
+        obj,
+        prop,
+        (() => {
+          let value = obj[prop];
+          return {
+            get: () => {
+              if (isCurrentScriptInstart(thisScript)) {
+                throw new ReferenceError(magic);
+              }
+              return value;
+            },
+            set(a: any) {
+              if (isCurrentScriptInstart(thisScript)) {
+                throw new ReferenceError(magic);
+              }
+              value = a;
+            },
+          };
+        })(),
+      );
+    });
+  },
+  [isCurrentScriptInstart],
+);
+
+/**
+ * Mock global objects from IL.
+ */
+const monkeyPatchNanoVisor = bundle((magic) => {
+  const HtmlStreamingMock = {
+    InsertTags(_: any, b: any) {
+      document.write(b);
+    },
+    MoveTagAndCleanUp() {
+      /* noop */
+    },
+    MoveTag() {
+      /* noop */
+    },
+    RemoveTags() {
+      /* noop */
+    },
+    InterceptNode() {
+      /* noop */
+    },
+    PatchBegin() {
+      /* noop */
+    },
+    PatchEnd() {
+      /* noop */
+    },
+    PatchInit() {
+      /* noop */
+    },
+    PatchK() {
+      /* noop */
+    },
+    ReloadWithNoHtmlStreaming() {
+      window.location.reload(true);
+    },
+    RemoveAttributes() {
+      /* noop */
+    },
+    UpdateAttributes() {
+      /* noop */
+    },
+    SendR() {
+      /* noop */
+    },
+    RemoveCurrentScript() {
+      /* noop */
+    },
+  };
+
+  const nanoVisorProxy = new Proxy(
+    {},
+    {
+      get(target, name) {
+        switch (name) {
+          case 'HtmlStreaming':
+            return HtmlStreamingMock;
+          default: {
+            // @ts-ignore
+            return target[name];
+          }
+        }
+      },
+      set(target, name, value) {
+        switch (name) {
+          case 'CanRun':
+            // @ts-ignore
+            target.CanRun = () => false;
+            break;
+          default:
+            // @ts-ignore
+            target[name] = value;
+        }
+        return true;
+      },
+    },
+  );
+
+  let instartInit: any;
+  Object.defineProperty(window, '_bcm_il', { value: true });
+  Object.defineProperty(window, 'I10C', { value: nanoVisorProxy });
+  Object.defineProperty(window, 'I11C', { value: nanoVisorProxy });
+  Object.defineProperty(window, 'INSTART', {
+    value: new Proxy(
+      {},
+      {
+        get(target, name) {
+          switch (name) {
+            case 'Init':
+              return (a: any) => {
+                if (
+                  a instanceof Object &&
+                  typeof a.nanovisorGlobalNameSpace === 'string' &&
+                  a.nanovisorGlobalNameSpace !== ''
+                ) {
+                  // @ts-ignore
+                  window[a.nanovisorGlobalNameSpace] = nanoVisorProxy;
+                }
+
+                a.disableInjectionXhr = true;
+                a.enableHtmlStreaming = false;
+                a.enableQSCallDiffComputationConfig = false;
+                a.enableQuerySelectorMonitoring = false;
+                a.partialImage = false;
+                a.rum = false;
+                a.serveNanovisorSameDomain = false;
+                a.useWrapper = false;
+                a.virtualDomains = 0;
+                a.virtualizeDomains = [];
+
+                if (instartInit !== undefined) {
+                  instartInit(a);
+                }
+              };
+            default:
+              // @ts-ignore
+              if (target[name] === undefined) {
+                throw new Error(magic);
+              }
+              // @ts-ignore
+              return target[name];
+          }
+        },
+        set(target, name, value) {
+          switch (name) {
+            case 'Init':
+              instartInit = value;
+              break;
+            default:
+              // @ts-ignore
+              target[name] = value;
+          }
+          return true;
+        },
+      },
+    ),
+  });
+});
+
+export default function instart(window: Window): void {
+  // NOTE: this list was partially borrowed from uBlockExtra and AdGuard
+  if (
+    [
+      'afterellen.com',
+      'allakhazam.com',
+      'americanphotomag.com',
+      'atvrider.com',
+      'baggersmag.com',
+      'baltimoresun.com',
+      'boatingmag.com',
+      'boston.com',
+      'cafemom.com',
+      'calgaryherald.com',
+      'calgarysun.com',
+      'capitalgazette.com',
+      'carrollcountytimes.com',
+      'cattime.com',
+      'cbssports.com',
+      'celebslam.com',
+      'celebuzz.com',
+      'chicagotribune.com',
+      'chowhound.com',
+      'chron.com',
+      'chroniclelive.co.uk',
+      'citypaper.com',
+      'cnet.com',
+      'comingsoon.net',
+      'computershopper.com',
+      'courant.com',
+      'craveonline.com',
+      'cruisingworld.com',
+      'csgoutpost.com',
+      'ctnow.com',
+      'cycleworld.com',
+      'dailydot.com',
+      'dailypress.com',
+      'dayzdb.com',
+      'deathandtaxesmag.com',
+      'delmartimes.net',
+      'destinationweddingmag.com',
+      'dirtrider.com',
+      'diversitybestpractices.com',
+      'dogtime.com',
+      'dotaoutpost.com',
+      'download.cnet.com',
+      'edmontonjournal.com',
+      'edmontonsun.com',
+      'edmunds.com',
+      'emedicinehealth.com',
+      'esohead.com',
+      'everquest.allakhazam.com',
+      'everydayhealth.com',
+      'extremetech.com',
+      'fieldandstream.com',
+      'financialpost.com',
+      'floridatravellife.com',
+      'flyingmag.com',
+      'focus.de',
+      'gamepedia.com',
+      'gamerevolution.com',
+      'gamespot.com',
+      'geek.com',
+      'gofugyourself.com',
+      'growthspotter.com',
+      'hearthhead.com',
+      'hockeysfuture.com',
+      'hotbikeweb.com',
+      'hoylosangeles.com',
+      'ibtimes.com',
+      'idigitaltimes.com',
+      'ign.com',
+      'infinitiev.com',
+      'islands.com',
+      'lajollalight.com',
+      'laptopmag.com',
+      'latintimes.com',
+      'leaderpost.com',
+      'legacy.com',
+      'lifewire.com',
+      'livescience.com',
+      'lolking.net',
+      'mamaslatinas.com',
+      'marlinmag.com',
+      'mcall.com',
+      'medicaldaily.com',
+      'medicinenet.com',
+      'metacritic.com',
+      'metrolyrics.com',
+      'mmo-champion.com',
+      'momtastic.com',
+      'montrealgazette.com',
+      'motorcyclecruiser.com',
+      'motorcyclistonline.com',
+      'motortrend.com',
+      'msn.com',
+      'musicfeeds.com.au',
+      'mustangandfords.com',
+      'mysanantonio.com',
+      'nasdaq.com',
+      'nationalpost.com',
+      'newsarama.com',
+      'newsweek.com',
+      'opshead.com',
+      'orlandosentinel.com',
+      'ottawacitizen.com',
+      'ottawasun.com',
+      'outdoorlife.com',
+      'pcmag.com',
+      'playstationlifestyle.net',
+      'popphoto.com',
+      'popsci.com',
+      'ranchosantafereview.com',
+      'range365.com',
+      'ranker.com',
+      'realclearpolitics.com',
+      'realitytea.com',
+      'redeyechicago.com',
+      'salon.com',
+      'saltwatersportsman.com',
+      'sandiegouniontribune.com',
+      'saveur.com',
+      'scubadiving.com',
+      'scubadivingintro.com',
+      'seattlepi.com',
+      'sfgate.com',
+      'sherdog.com',
+      'slate.com',
+      'slickdeals.net',
+      'southflorida.com',
+      'space.com',
+      'spin.com',
+      'sporcle.com',
+      'sportdiver.com',
+      'sportfishingmag.com',
+      'sportingnews.com',
+      'sportrider.com',
+      'spox.com',
+      'stereogum.com',
+      'streetchopperweb.com',
+      'sun-sentinel.com',
+      'superherohype.com',
+      'superstreetbike.com',
+      'tenplay.com.au',
+      'tf2outpost.com',
+      'thebalance.com',
+      'thefashionspot.com',
+      'thefrisky.com',
+      'theprovince.com',
+      'thespruce.com',
+      'thestarphoenix.com',
+      'thesuperficial.com',
+      'thoughtcatalog.com',
+      'thoughtco.com',
+      'timeanddate.com',
+      'timesunion.com',
+      'tmn.today',
+      'tomsguide.com',
+      'tomsguide.fr',
+      'tomshardware.co.uk',
+      'tomshardware.com',
+      'tomshardware.de',
+      'tomshardware.fr',
+      'torontosun.com',
+      'totalbeauty.com',
+      'trustedreviews.com',
+      'tv.com',
+      'tvguide.com',
+      'tvtropes.org',
+      'twincities.com',
+      'utvdriver.com',
+      'vancouversun.com',
+      'vg.no',
+      'vibe.com',
+      'wakeboardingmag.com',
+      'washingtonpost.com',
+      'waterskimag.com',
+      'webmd.com',
+      'wikia.com',
+      'windowscentral.com',
+      'windsorstar.com',
+      'winnipegsun.com',
+      'workingmother.com',
+      'wowhead.com',
+      'wrestlezone.com',
+      'xda-developers.com',
+      'yachtingmagazine.com',
+      'zam.com',
+    ].indexOf(getWindowHostname(window)) !== -1
+  ) {
+    // Un-comment to debug InstartLogic
+    // protectConsole(window);
+
+    swallowOwnErrors(window, contentScriptMagic);
+    monkeyPatchNanoVisor(window, contentScriptMagic);
+    shieldPropertiesFromInstart(window, contentScriptMagic);
+  }
+}
diff --git a/src/content/helpers.ts b/src/content/helpers.ts
new file mode 100644
index 0000000000..41ea90bd80
--- /dev/null
+++ b/src/content/helpers.ts
@@ -0,0 +1,35 @@
+/**
+ * This module exports a list of helpers which can be used in content script.
+ * *DO NOT* use these as part of scriptlets as these might not be available in
+ * the context of pages.
+ */
+
+export function getWindowHostname(window: Window) {
+  const strip = (hostname: string): string => {
+    if (hostname.startsWith('www.')) {
+      return hostname.slice(4);
+    }
+    return hostname;
+  };
+
+  let win = window;
+
+  while (win) {
+    const hostname = win.location.hostname;
+    if (hostname !== '') {
+      return strip(hostname);
+    }
+
+    if (win === window.parent) {
+      break;
+    }
+
+    win = win.parent;
+  }
+
+  return '';
+}
+
+export const magic = Math.abs((Date.now() * 524287) ^ ((Math.random() * 524287) >>> 0)).toString(
+  16,
+);
diff --git a/src/content/injection.ts b/src/content/injection.ts
new file mode 100644
index 0000000000..1ed103a364
--- /dev/null
+++ b/src/content/injection.ts
@@ -0,0 +1,92 @@
+/**
+ * Wrap a self-executing script into a block of custom logic to remove the
+ * script tag once execution is terminated. This can be useful to not leave
+ * traces in the DOM after injections.
+ */
+function autoRemoveScript(script: string): string {
+  return `
+try {
+  ${script}
+} catch (ex) { }
+
+(function() {
+  var currentScript = document.currentScript;
+  var parent = currentScript && currentScript.parentNode;
+
+  if (parent) {
+    parent.removeChild(currentScript);
+  }
+})();
+  `;
+}
+
+/**
+ * Given a self-executing script as well as a list of dependencies (function
+ * which are required by the injected script), create a script which contains
+ * both the dependencies (as scoped functions) and the script.
+ */
+function wrapCallableInContext(script: string, deps: Array<(...args: any[]) => any> = []): string {
+  return `
+${deps.map((dep) => `const ${dep.name} = ${dep.toString()};`).join('\n')}
+${script}
+  `;
+}
+
+/**
+ * Given a function which can accept arguments, serialize it into a string (as
+ * well as its argument) so that it will automatically execute upon injection.
+ */
+function autoCallFunction(fn: (...args: any[]) => void, ...args: any[]): string {
+  return `
+try {
+  (${fn.toString()})(${args.map((arg) => JSON.stringify(arg)).join(', ')});
+} catch (ex) {  };`;
+}
+
+export function blockScript(filter: string, doc: Document): void {
+  const filterRE = new RegExp(filter);
+  doc.addEventListener('beforescriptexecute', (ev) => {
+    const target = ev.target as HTMLElement;
+    if (target.textContent && filterRE.test(target.textContent)) {
+      ev.preventDefault();
+      ev.stopPropagation();
+    }
+  });
+}
+
+export function injectCSSRule(rule: string, doc: Document): void {
+  const css = doc.createElement('style');
+  css.type = 'text/css';
+  css.id = 'cliqz-adblokcer-css-rules';
+  const parent = doc.head || doc.documentElement;
+  if (parent !== null) {
+    parent.appendChild(css);
+    css.appendChild(doc.createTextNode(rule));
+  }
+}
+
+export function injectScript(s: string, doc: Document): void {
+  const script = doc.createElement('script');
+  script.type = 'text/javascript';
+  script.id = 'cliqz-adblocker-script';
+  script.async = false;
+  script.appendChild(doc.createTextNode(autoRemoveScript(s)));
+
+  // Insert node
+  const parent = doc.head || doc.documentElement;
+  if (parent !== null) {
+    parent.appendChild(script);
+  }
+}
+
+/**
+ * Given a scriptlet (as well as optional dependencies: symbols which must be
+ * available in the scope for this scriptlet to do its job), returns a callback
+ * which needs to be called with the desired window as well as optional
+ * arguments for the scriptlet. The script will be injected in the head of
+ * window's document as a self-executing, self-erasing script element.
+ */
+export function bundle(fn: (...args: any[]) => void, deps: Array<(...args: any[]) => any> = []) {
+  return (window: Window, ...args: any[]) =>
+    injectScript(wrapCallableInContext(autoCallFunction(fn, ...args), deps), window.document);
+}
diff --git a/src/cosmetics-injection.ts b/src/cosmetics-injection.ts
index e3e65034b2..60f525fcda 100644
--- a/src/cosmetics-injection.ts
+++ b/src/cosmetics-injection.ts
@@ -1,11 +1,13 @@
+import injectCircumvention from './content/circumvention';
+import { blockScript, injectCSSRule, injectScript } from './content/injection';
 
 // We need this as `MutationObserver` is currently not part of the `Window` type
 // provided by typescript, although it should be! This will be erased at compile
 // time so it has no impact on produced code.
 declare global {
-    interface Window {
-        MutationObserver?: typeof MutationObserver;
-   }
+  interface Window {
+    MutationObserver?: typeof MutationObserver;
+  }
 }
 
 interface IMessageFromBackground {
@@ -15,67 +17,6 @@ interface IMessageFromBackground {
   styles: string[];
 }
 
-function injectCSSRule(rule: string, doc: Document): void {
-  const css = doc.createElement('style');
-  css.type = 'text/css';
-  css.id = 'cliqz-adblokcer-css-rules';
-  const parent = doc.head || doc.documentElement;
-  if (parent !== null) {
-    parent.appendChild(css);
-    css.appendChild(doc.createTextNode(rule));
-  }
-}
-
-function injectScript(s: string, doc: Document): void {
-  // Wrap script so that it removes itself when the execution is over.
-  const autoRemoveScript = `
-    try {
-      ${s}
-    } catch (ex) { }
-
-    (function() {
-      var currentScript = document.currentScript;
-      var parent = currentScript && currentScript.parentNode;
-
-      if (parent) {
-        parent.removeChild(currentScript);
-      }
-    })();
-  `;
-
-  // Create node
-  const script = doc.createElement('script');
-  script.type = 'text/javascript';
-  script.id = 'cliqz-adblocker-script';
-  script.appendChild(doc.createTextNode(autoRemoveScript));
-
-  // Insert node
-  const parent = doc.head || doc.documentElement;
-  if (parent !== null) {
-    parent.appendChild(script);
-  }
-}
-
-function blockScript(filter: string, doc: Document): void {
-  const filterRE = new RegExp(filter);
-  doc.addEventListener('beforescriptexecute', ev => {
-    const target = ev.target as HTMLElement;
-    if (target.textContent && filterRE.test(target.textContent)) {
-      ev.preventDefault();
-      ev.stopPropagation();
-    }
-  });
-}
-
-export function overrideUserAgent(): void {
-  const script = () => {
-    Object.defineProperty(navigator, 'userAgent', {
-      get: () => 'Mozilla/5.0 Gecko Firefox',
-    });
-  };
-  injectScript(`(${script.toString()})()`, window.document);
-}
-
 /**
  * Takes care of injecting cosmetic filters in a given window. Responsabilities:
  * - Inject scripts.
@@ -105,8 +46,11 @@ export default class CosmeticInjection {
   private observedNodes: Set<string>;
   private mutationObserver: MutationObserver | null;
 
-  constructor(window: Window, backgroundAction: (action: string, ...args: any[]) => Promise<void>,
-              useMutationObserver = true) {
+  constructor(
+    window: Window,
+    backgroundAction: (action: string, ...args: any[]) => Promise<void>,
+    useMutationObserver = true,
+  ) {
     this.window = window;
     this.backgroundAction = backgroundAction;
 
@@ -139,7 +83,16 @@ export default class CosmeticInjection {
     }
   }
 
-  public handleResponseFromBackground({ active, scripts, blockedScripts, styles }: IMessageFromBackground) {
+  public injectCircumvention(): void {
+    injectCircumvention(this.window);
+  }
+
+  public handleResponseFromBackground({
+    active,
+    scripts,
+    blockedScripts,
+    styles,
+  }: IMessageFromBackground) {
     if (!active) {
       this.unload();
       return;
@@ -204,7 +157,7 @@ export default class CosmeticInjection {
    * cosmetic filters to inject in the page.
    */
   private onMutation(mutations: Array<{ target: Node }>) {
-    let targets: Set<Node> = new Set(mutations.map(m => m.target).filter(t => t));
+    let targets: Set<Node> = new Set(mutations.map((m) => m.target).filter((t) => t));
 
     // TODO - it might be necessary to inject scripts, CSS and block scripts
     // from here into iframes with no src. We could first inject/block
@@ -231,7 +184,7 @@ export default class CosmeticInjection {
 
     // Collect nodes of targets
     const nodeInfo = new Set();
-    targets.forEach(target => {
+    targets.forEach((target) => {
       const nodes = (target as HTMLElement).querySelectorAll('*');
       for (let i = 0; i < nodes.length; i += 1) {
         const node = nodes[i] as HTMLElement;
@@ -258,7 +211,7 @@ export default class CosmeticInjection {
         }
 
         if (node.className && node.className.split) {
-          node.className.split(' ').forEach(name => {
+          node.className.split(' ').forEach((name) => {
             const selector = `.${name}`;
             if (!this.observedNodes.has(selector)) {
               nodeInfo.add(selector);
@@ -278,7 +231,7 @@ export default class CosmeticInjection {
   private startObserving() {
     // Attach mutation observer in case the DOM is mutated.
     if (this.window.MutationObserver !== undefined) {
-      this.mutationObserver = new this.window.MutationObserver(mutations =>
+      this.mutationObserver = new this.window.MutationObserver((mutations) =>
         this.onMutation(mutations),
       );
       this.mutationObserver.observe(this.window.document, {
diff --git a/src/fetch.ts b/src/fetch.ts
index 574ddc8977..3560779052 100644
--- a/src/fetch.ts
+++ b/src/fetch.ts
@@ -2,24 +2,78 @@ function fetchResource(url: string): Promise<string> {
   return fetch(url).then((response: any) => response.text());
 }
 
-const defaultLists = [
-  // 'https://easylist-downloads.adblockplus.org/antiadblockfilters.txt',
-  // 'https://easylist-downloads.adblockplus.org/easylistgermany.txt',
-  'https://easylist.to/easylist/easylist.txt',
-  'https://easylist.to/easylist/easyprivacy.txt',
-  'https://pgl.yoyo.org/adservers/serverlist.php?hostformat=adblockplus&showintro=1&mimetype=plaintext',
-  'https://raw.githubusercontent.com/uBlockOrigin/uAssets/master/filters/badware.txt',
-  'https://raw.githubusercontent.com/uBlockOrigin/uAssets/master/filters/filters.txt',
-  'https://raw.githubusercontent.com/uBlockOrigin/uAssets/master/filters/privacy.txt',
-  'https://raw.githubusercontent.com/uBlockOrigin/uAssets/master/filters/resource-abuse.txt',
-  'https://raw.githubusercontent.com/uBlockOrigin/uAssets/master/filters/unbreak.txt',
+const enum Category {
+  Privacy,
+  Ads,
+  Unbreak,
+  Circumvention,
+  Country,
+  Misc,
+}
+
+const lists = [
+  {
+    category: Category.Unbreak,
+    enabledByDefault: true,
+    url: 'https://easylist-downloads.adblockplus.org/antiadblockfilters.txt',
+  },
+  {
+    category: Category.Country,
+    country: 'de',
+    enabledByDefault: false,
+    url: 'https://easylist-downloads.adblockplus.org/easylistgermany.txt',
+  },
+  {
+    category: Category.Ads,
+    enabledByDefault: true,
+    url: 'https://easylist.to/easylist/easylist.txt',
+  },
+  {
+    category: Category.Privacy,
+    enabledByDefault: false,
+    url: 'https://easylist.to/easylist/easyprivacy.txt',
+  },
+  {
+    category: Category.Ads,
+    enabledByDefault: false,
+    url:
+      'https://pgl.yoyo.org/adservers/serverlist.php?hostformat=adblockplus&showintro=1&mimetype=plaintext',
+  },
+  {
+    category: Category.Misc,
+    enabledByDefault: false,
+    url: 'https://raw.githubusercontent.com/uBlockOrigin/uAssets/master/filters/badware.txt',
+  },
+  {
+    category: Category.Ads,
+    enabledByDefault: true,
+    url: 'https://raw.githubusercontent.com/uBlockOrigin/uAssets/master/filters/filters.txt',
+  },
+  {
+    category: Category.Privacy,
+    enabledByDefault: false,
+    url: 'https://raw.githubusercontent.com/uBlockOrigin/uAssets/master/filters/privacy.txt',
+  },
+  {
+    category: Category.Misc,
+    enabledByDefault: true,
+    url:
+      'https://raw.githubusercontent.com/uBlockOrigin/uAssets/master/filters/resource-abuse.txt',
+  },
+  {
+    category: Category.Unbreak,
+    enabledByDefault: true,
+    url: 'https://raw.githubusercontent.com/uBlockOrigin/uAssets/master/filters/unbreak.txt',
+  },
 ];
 
 /**
- * Fetch latest version of default blocking lists.
+ * Fetch latest version of enabledByDefault blocking lists.
  */
-export function fetchLists(lists: string[] = defaultLists): Promise<string[]> {
-  return Promise.all(lists.map(fetchResource));
+export function fetchLists(): Promise<string[]> {
+  return Promise.all(
+    lists.filter(({ enabledByDefault }) => enabledByDefault).map(({ url }) => fetchResource(url)),
+  );
 }
 
 /**
diff --git a/src/parsing/network-filter.ts b/src/parsing/network-filter.ts
index b89a7d96e4..d1d612b7c3 100644
--- a/src/parsing/network-filter.ts
+++ b/src/parsing/network-filter.ts
@@ -732,6 +732,12 @@ export function parseNetworkFilter(rawLine: string): NetworkFilter | null {
 
           break;
         }
+        case 'badfilter':
+          // TODO - how to handle those, if we start in mask, then the id will
+          // differ from the other filter. We could keep original line. How do
+          // to eliminate thos efficiently? They will probably endup in the same
+          // bucket, so maybe we could do that on a per-bucket basis?
+          return null;
         case 'important':
           // Note: `negation` should always be `false` here.
           if (negation) {
diff --git a/tsconfig.json b/tsconfig.json
index ca651e5c36..7fbc4fdd79 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -2,9 +2,11 @@
   "compilerOptions": {
     "declaration": true,
     "declarationDir": "dist/types",
-    "types": ["jest", "node", "chrome"],
+    "types": ["jest", "node", "chrome", "jsdom"],
     "target": "ES3",
-    "lib": ["ES6", "DOM"],
+    "lib": ["es2015", "ES6", "DOM"],
+    "module": "ES6",
+    "outDir": "build",
     "newLine": "lf",
     "removeComments": true,
     "moduleResolution": "Node",