Apple stops signing iOS 15.3.1 after iOS 15.4 release, downgrade no longer possible

Following the release of iOS 15.4 on March 14, Apple has stopped signing iOS 15.3.1, the previously available iOS version released in February. Because iOS 15.3.1 is no longer signed, you can't downgrade to that version of iOS if you've updated to iOS 15.4.

Apple typically stops signing older versions of software updates after a new version is released to encourage customers to keep their operating systems up to date, so it's not unusual for iOS 15.3.1 to no longer be signed .

iOS 15.3.1 is a bug-fix update for a WebKit vulnerability, while iOS 15.4 is a major update that adds new emoji characters, Face ID with masks, and a ton of other features. Apple also stopped signing tvOS 15.3.

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