Carrier updates might have some power i'm not aware of on iOS (they pop up saying "do you want to update carrier settings" with simple yes/no options), but regular iOS software updates do require connection to Apple servers and the firmware itself also has to be signed by Apple.
The carrier setting thing hasn't ever been use for a jailbreak exploit AFAIK so chances are it's not a good attack vector.
From your other comment:
> But it mentions the option of wiping baseband firmware
iOS also has signature verification for its baseband, since trying to load an incompatible one during a downgrade[0] breaks Face ID / Touch ID.
But ya, this is all "trust apple to not do anything". They've made a good stance with refusing the FBI request[1], but the FBI got into the phone anyways[2].
The carrier setting thing hasn't ever been use for a jailbreak exploit AFAIK so chances are it's not a good attack vector.
From your other comment:
> But it mentions the option of wiping baseband firmware
iOS also has signature verification for its baseband, since trying to load an incompatible one during a downgrade[0] breaks Face ID / Touch ID.
But ya, this is all "trust apple to not do anything". They've made a good stance with refusing the FBI request[1], but the FBI got into the phone anyways[2].
0: https://github.com/tihmstar/futurerestore
1: https://news.ycombinator.com/item?id=11116274
2: https://venturebeat.com/2016/03/28/u-s-government-gains-acce...