diff -up firefox-48.0/browser/app/profile/firefox.js.addons firefox-48.0/browser/app/profile/firefox.js
--- firefox-48.0/browser/app/profile/firefox.js.addons	2016-07-26 10:56:48.598900568 +0200
+++ firefox-48.0/browser/app/profile/firefox.js	2016-07-26 11:05:45.199789758 +0200
@@ -94,7 +94,8 @@ pref("extensions.systemAddon.update.url"
 
 // 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);
 // Scopes to scan for changes at startup.
 pref("extensions.startupScanScopes", 0);