do not allow invalid hazardous string as section name

ini.js

@@ -80,6 +80,12 @@ function decode (str) {
     if (!match) return
     if (match[1] !== undefined) {
       section = unsafe(match[1])
+      if (section === '__proto__') {
+        // not allowed
+        // keep parsing the section, but don't attach it.
+        p = {}
+        return
+      }
       p = out[section] = out[section] || {}
       return
     }
@@ -94,6 +100,7 @@ function decode (str) {
     // Convert keys with '[]' suffix to an array
     if (key.length > 2 && key.slice(-2) === '[]') {
       key = key.substring(0, key.length - 2)
+      if (key === '__proto__') return
       if (!p[key]) {
         p[key] = []
       } else if (!Array.isArray(p[key])) {
@@ -125,6 +132,7 @@ function decode (str) {
     var l = parts.pop()
     var nl = l.replace(/\\\./g, '.')
     parts.forEach(function (part, _, __) {
+      if (part === '__proto__') return
       if (!p[part] || typeof p[part] !== 'object') p[part] = {}
       p = p[part]
     })

test/proto.js

@@ -0,0 +1,45 @@
+var ini = require('../')
+var t = require('tap')
+
+var data = `
+__proto__ = quux
+foo = baz
+[__proto__]
+foo = bar
+[other]
+foo = asdf
+[kid.__proto__.foo]
+foo = kid
+[arrproto]
+hello = snyk
+__proto__[] = you did a good job
+__proto__[] = so you deserve arrays
+thanks = true
+`
+var res = ini.parse(data)
+t.deepEqual(res, {
+  foo: 'baz',
+  other: {
+    foo: 'asdf',
+  },
+  kid: {
+    foo: {
+      foo: 'kid',
+    },
+  },
+  arrproto: {
+    hello: 'snyk',
+    thanks: true,
+  },
+})
+t.equal(res.__proto__, Object.prototype)
+t.equal(res.kid.__proto__, Object.prototype)
+t.equal(res.kid.foo.__proto__, Object.prototype)
+t.equal(res.arrproto.__proto__, Object.prototype)
+t.equal(Object.prototype.foo, undefined)
+t.equal(Object.prototype[0], undefined)
+t.equal(Object.prototype['0'], undefined)
+t.equal(Object.prototype[1], undefined)
+t.equal(Object.prototype['1'], undefined)
+t.equal(Array.prototype[0], undefined)
+t.equal(Array.prototype[1], undefined)