diff -up firefox-43.0/firefox-43.0/browser/app/profile/firefox.js.addons firefox-43.0/firefox-43.0/browser/app/profile/firefox.js
--- firefox-43.0/browser/app/profile/firefox.js.addons	2015-12-10 10:18:32.942990945 +0100
+++ firefox-43.0/browser/app/profile/firefox.js	2015-12-10 10:22:36.435169388 +0100
@@ -71,7 +71,8 @@ pref("extensions.hotfix.certs.2.sha1Fing
 
 // Disable add-ons that are not installed by the user in all scopes by default.
 // See the SCOPE constants in AddonManager.jsm for values to use here.
-pref("extensions.autoDisableScopes", 15);
+pref("extensions.autoDisableScopes", 0);
+pref("extensions.showMismatchUI", false);
 
 // Require signed add-ons by default
 pref("xpinstall.signatures.required", true);