Reminds me of how I ended up with a U2 album on my iPhone. I never put those files there not asked for them or gave permission. Made me wonder what else could they plant on my phone.
I mean, you're talking about a bit of a different thing here--something done by the operating system and hardware vendor.
So the answer would be "literally anything". Apple could push an update tomorrow that bricked your phone, turned it into a listening device, caused it to _only_ play that U2 album, etc. Ditto for Google (Android), Microsoft (Windows), etc.
