Apple suddenly shut down the iOS 15.4.1 verification channel
For those who have upgraded to iOS 15.5, please note that Apple has disabled the verification channel for iOS 15.4.1, which means that it is no longer possible to downgrade from 15.5.
IOS 15.4.1 was released at the end of March, while the official version of iOS 15.5 was only released last week. Apple is already testing iOS 15.6.
In iOS 15.4.1, Apple addressed a battery drain that was too fast, as well as the AppleAVD bug, which allows applications to access the kernel for arbitrary code execution.
However, according to Apple, users are advised to update to iOS 15.5 as soon as possible, which not only fixes more than two dozen bugs (most of which trigger remote execution vulnerabilities), but also upgrades to the baseband version to improve phone signal, especially the iPhone 12/13, and improve battery life.
And if you don't mind the beta, iOS 16 will make its debut at WWDC next week.