Jailbreak regulars will be the hardest hit by this measure.
Shortly after the release of a new update, Apple allows its iPhone users to fall back to the previous version of the operating system in case of problems with the new update, such as bugs or a significant decrease in battery life. Others use the downgrade to jailbreak their iPhone and thus benefit from locked functions and applications.
Apple rolled out iOS 15.4 a few days ago, bringing new features like using Face ID with a mask, Universal Control, new emojis, and Tap to Pay, the option that turns your iPhone into a payment terminal. . An update that succeeded version 15.3.1 of iOS that provides additional security for WebKit (the Safari engine) and braille terminals that were not always responding correctly.
As soon as iOS 15.4 is in use on all iPhones, Apple no longer signs iOS 15.3.1. In other words, it was removed by Apple. Anyone who is dissatisfied with iOS 15.4 cannot return to the previous version, which has been available since mid-February. Jailbreakers could go back to iOS 15.3.1 to hack their iPhone.
In addition to iOS 15.3.1, Apple also no longer signed tvOS 15.3, which could also have been used for jailbreaks.