Apple no longer signs iOS 15.4 after later iOS 15.4.1 update
Apple updated iOS & iPadOS 15.4.1 last week to address a power drain issue that had been extensively reported by a large number of customers on iOS & iPadOS 15.4 as well as to repair several security flaws.
After a week, Apple has finally closed the signing window for the older iOS & iPadOS 15.4 firmware, preventing most forced upgrades or downgrades to this version unless using DelayOTA or futurerestore.
Apple unsigns outdated software on a regular basis, so this should come as no surprise. Indeed, it benefits Apple by increasing the adoption of new firmware and satisfying shareholders while also guaranteeing that consumers are taking use of the latest features and updates.
As there is presently no jailbreak tool that supports iOS or iPadOS 15.4, this announcement has little influence on the jailbreak community. The Odyssey Team is presently working on a jailbreak that supports iOS & iPadOS 15.0-15.1.1, and a future release to checkra1n may provide compatibility for all versions of iOS & iPadOS 15.
Of course, firmware downgrades are not limited to jailbreakers; new firmware upgrades can occasionally create flaws, prompting some users to downgrade in order to fix their devices.
If you’re ever interested about which version(s) of iOS or iPadOS are signed for your device(s), you can easily find out by visiting the ipsw.me website. Additionally, you may get firmware straight from our downloads page.