add network.http.referer.XOriginPolicy: 2 in addition to referer spoo…

…fing:

Users wanting to disable referer spoofing to workaround listed problems will still be protected against disclosing previously visited pages to target domains when clicking on a link

README.md

@@ -233,7 +233,8 @@ HTTP protocol related entries. This affects cookies, the user agent, referer and
 * Enable CSP 1.1 script-nonce directive support [ [1](https://bugzilla.mozilla.org/show_bug.cgi?id=855326) ]
 * Enable Content Security Policy
 * Enable Subresource Integrity [ [1](https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity) [2](https://wiki.mozilla.org/Security/Subresource_Integrity) ]
-* Send a referer header with the target URI as the source [ [1](https://bugzilla.mozilla.org/show_bug.cgi?id=822869) ]
+* Send a referer header with the target URI as the source [ [1](https://bugzilla.mozilla.org/show_bug.cgi?id=822869) [2](https://github.com/pyllyukko/user.js/issues/227) ]
+* Don't send referer headers when following links across different domains [ [1](https://github.com/pyllyukko/user.js/issues/227) ]
 * Accept Only 1st Party Cookies [ [1](http://kb.mozillazine.org/Network.cookie.cookieBehavior#1) ]
 * Make sure that third-party cookies (if enabled) never persist beyond the session. [ [1](https://feeding.cloud.geek.nz/posts/tweaking-cookies-for-privacy-in-firefox/) [2](http://kb.mozillazine.org/Network.cookie.thirdparty.sessionOnly) [3](https://developer.mozilla.org/en-US/docs/Cookies_Preferences_in_Mozilla#network.cookie.thirdparty.sessionOnly) ]
 
@@ -378,6 +379,7 @@ Hardening your often implies a trade-off with ease-of-use and comes with reduced
 * Do No Track must be enabled manually
 * Spoofing referers breaks functionality on websites relying on authentic referer headers
 * Spoofing referers breaks visualisation of 3rd-party sites on the Lightbeam addon
+* Spoofing referers disables CSRF protection on some login pages not implementing origin-header/cookie+token based CSRF protection
 * Blocking 3rd-party cookies breaks a number of payment gateways
 * You can not view or inspect cookies when in private browsing: https://bugzilla.mozilla.org/show_bug.cgi?id=823941
 * Installing user.js will **remove your saved passwords** (https://github.com/pyllyukko/user.js/issues/27)

user.js

@@ -511,11 +511,17 @@ user_pref("security.sri.enable",				true);
 
 // PREF: Send a referer header with the target URI as the source
 // https://bugzilla.mozilla.org/show_bug.cgi?id=822869
+// https://github.com/pyllyukko/user.js/issues/227
 // NOTICE: Spoofing referers breaks functionality on websites relying on authentic referer headers
 // NOTICE: Spoofing referers breaks visualisation of 3rd-party sites on the Lightbeam addon
+// NOTICE: Spoofing referers disables CSRF protection on some login pages not implementing origin-header/cookie+token based CSRF protection
 // TODO: https://github.com/pyllyukko/user.js/issues/94, commented-out XOriginPolicy/XOriginTrimmingPolicy = 2 prefs
 user_pref("network.http.referer.spoofSource",			true);
 
+// PREF: Don't send referer headers when following links across different domains
+// https://github.com/pyllyukko/user.js/issues/227
+user_pref("network.http.referer.XOriginPolicy",		2);
+
 // PREF: Accept Only 1st Party Cookies
 // http://kb.mozillazine.org/Network.cookie.cookieBehavior#1
 // NOTICE: Blocking 3rd-party cookies breaks a number of payment gateways