Last week, Apple published iOS & iPadOS 15.4.1 and Apple stops signing iOS 15.4, which included a fix for the power depletion issue that had been reported by a large number of customers on iOS & iPadOS 15.4 as well as patches for certain security flaws. One week later, Apple has closed the signing window for the older iOS & iPadOS 15.4 firmware, a move that disables most forced upgrades or downgrades to this version unless with DelayOTA or future restore.
Apple stops signing iOS 15.4 following the newer iOS 15.4.1 software update
Apple unsigns older firmware on a regular basis, so this should come as no surprise. In fact, it benefits Apple by increasing the adoption of new firmware and gratifying shareholders while assuring that users have access to the most recent features and patches.
The fact that no jailbreak tool currently supports iOS or iPadOS 15.4 has little impact on the jailbreak community. The Odyssey Team is currently working on a jailbreak for iOS & iPadOS 15.0-15.1.1, with a future upgrade to checkra1n potentially supporting all versions of iOS & iPadOS 15 at some point.
Of course, jailbreakers aren’t the only ones who downgrade firmware; new firmware upgrades can often create flaws, prompting some users to downgrade in order to patch their devices.
If you’re ever curious about which version(s) of iOS or iPadOS are signed for your device(s), check out the ipsw.me website. Our downloads website also has firmware files available for download.