diff -up firefox-46.0/browser/app/profile/firefox.js.addons firefox-46.0/browser/app/profile/firefox.js
--- firefox-46.0/browser/app/profile/firefox.js.addons	2016-04-22 02:37:18.000000000 +0200
+++ firefox-46.0/browser/app/profile/firefox.js	2016-04-25 12:09:36.133479899 +0200
@@ -74,7 +74,8 @@ 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);
 
 // Require signed add-ons by default
 pref("xpinstall.signatures.required", true);
diff -up firefox-46.0/toolkit/mozapps/extensions/internal/XPIProvider.jsm.addons firefox-46.0/toolkit/mozapps/extensions/internal/XPIProvider.jsm
--- firefox-46.0/toolkit/mozapps/extensions/internal/XPIProvider.jsm.addons	2016-04-25 12:09:36.134479903 +0200
+++ firefox-46.0/toolkit/mozapps/extensions/internal/XPIProvider.jsm	2016-04-25 13:32:07.401769022 +0200
@@ -2679,6 +2679,9 @@ this.XPIProvider = {
           this.showUpgradeUI(addonsToUpdate);
           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) {