Probably all apps that has some voip calling functionality.
Whatsapp, messenger, viber (is that still a thing?) and similar
Edit, just saw
Unless they provide call or alarm functionality
So they should be safe
Possibly some security related apps to auth for banking and stuff, not sure how they work behind the scenes.
Same goes for some 2FA apps i guess?
As for your firefox issues, thats pretty trivial to fix by adding some CSS in usercontent.css/userchrome.css
See here for some examples: MrOtherGuy/firefox-csshacks