Apple Stops Signing iOS 17.5.1, Downgrading No Longer an Option
Apple today stopped signing iOS 17.5.1, preventing iPhone users from downgrading to that version of iOS. The update is no longer being signed after the July 29 release of iOS 17.6.

Apple often stops signing an older version of iOS, usually within a week or two after a new version is released. When an update is no longer signed, it can't be installed on an iPhone due to a server-side software verification check.
This policy encourages users to keep their operating systems up to date, ensuring they have the latest security enhancements.
iOS 17.5.1 addressed a corruption bug that could cause deleted photos to reappear on an iPhone. There were no notable features in the iOS 17.6 update, with Apple adding unspecified bug fixes and security updates.
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