Apple ceases iOS 15.3 code signing following iOS 15.3.1 launch

On Thursday, Apple stopped signing iOS 15.3, effectively blocking downgrades for users who are running iOS 15.3.1 or later.

The end of code signing for iOS 15.3 comes about eight days after Apple released iOS 15.3.1 to the public.

iOS 15.3.1 was a minor update with bug fixes and security patches. One notable addition in the update was a fix for a WebKit flaw that could have allowed maliciously crafted web content to lead to arbitrary code execution. Apple says it's aware of reports that the vulnerability may have been exploited in the wild.

The iOS 15.3 update that's no longer available as of Thursday was released back in January. Like the current point release, it mainly focused on under-the-hood improvements and bug fixes.

Apple routinely stops signing legacy code after the release of a new iOS build to protect customers from nefarious actors attempting to take advantage of newly discovered vulnerabilities. Preventing users from downloading older code also allows Apple to keep more iOS devices on the latest, feature-rich software.

With the stop in code signing, iOS 15.3.1 is now the only viable software update for iPhone and iPad users. The Cupertino tech giant is currently beta testing iOS 15.4, which includes updates to Face ID and a framework for Apple's upcoming Tap to Pay With iPhone.