diff -up mozilla-release/browser/app/profile/firefox.js.addons mozilla-release/browser/app/profile/firefox.js

--- mozilla-release/browser/app/profile/firefox.js.addons	2015-08-06 12:57:11.459795815 +0200

+++ mozilla-release/browser/app/profile/firefox.js	2015-08-06 13:01:55.045869605 +0200

@@ -69,7 +69,8 @@ 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);

 // Don't require signed add-ons by default

 pref("xpinstall.signatures.required", false);

diff -up mozilla-release/toolkit/mozapps/extensions/internal/XPIProvider.jsm.addons mozilla-release/toolkit/mozapps/extensions/internal/XPIProvider.jsm

--- mozilla-release/toolkit/mozapps/extensions/internal/XPIProvider.jsm.addons	2015-08-04 22:24:47.000000000 +0200

+++ mozilla-release/toolkit/mozapps/extensions/internal/XPIProvider.jsm	2015-08-06 12:57:11.461795823 +0200

@@ -2293,11 +2293,7 @@ this.XPIProvider = {

       AddonManagerPrivate.markProviderSafe(this);

-      if (aAppChanged === undefined) {

-        // For new profiles we will never need to show the add-on selection UI

-        Services.prefs.setBoolPref(PREF_SHOWN_SELECTION_UI, true);

-      }

-      else if (aAppChanged && !this.allAppGlobal &&

+      if (aAppChanged && !this.allAppGlobal &&

                Preferences.get(PREF_EM_SHOW_MISMATCH_UI, true)) {

         if (!Preferences.get(PREF_SHOWN_SELECTION_UI, false)) {

           // Flip a flag to indicate that we interrupted startup with an interactive prompt

@@ -2317,6 +2313,9 @@ this.XPIProvider = {

             flushCaches = true;

           }

         }

+      } else {

+        // For new profiles we will never need to show the add-on selection UI

+        Services.prefs.setBoolPref(PREF_SHOWN_SELECTION_UI, true);

       }

       if (flushCaches) {