Apple Stops Signing iOS 13.5 After Releasing iOS 13.5.1 With Jailbreak Patch
Following the release of iOS 13.5.1 on June 1, Apple has stopped signing iOS 13.5, which means downgrading to that version of iOS is no longer possible.
iOS 13.5.1 included a fix for the vulnerability that enabled the unc0ver jailbreaking tool that was released on May 24. The unc0ver jailbreak was compatible with all versions of iOS up to iOS 13.5, but since it has been patched in iOS 13.5.1, it is not possible to jailbreak a device running the iOS 13.5.1 update.
Apple released a similar security fix for tvOS, watchOS, and macOS, patching the vulnerability across all devices.
Apple routinely stops signing older versions of software updates after new releases come out in order to encourage customers to keep their operating systems up to date.
iOS 13.5.1, with the security fix, is the only current publicly available version of iOS that can be installed on iPhones and iPads. Apple has also seeded the first betas of upcoming iOS and iPadOS 13.5.5 updates to developers and public beta testers.