Apple has finally stopped signing the iOS 8.4 firmware after less than two weeks of the release of iOS 8.4.1. Once Apple stops signing a software version, it means that user will no longer be able to restore that version of iOS onto his/her iPhone, iPad, or iPod Touch.
Since Apple has closed the iOS 8.4 signing windows, you can no longer downgrade from iOS 8.4.1 to iOS 8.4 and re-jailbreak your iPhone, iPad, or iPod Touch either using TaiG jailbreak or PP jailbreak tool.
While the signing window does not concern the majority of the iOS users, but it’s of great importance for the jailbreak users out there. For instance, downgrading becomes very useful when a previous version of iOS is jailbreak-able, but not the latest version. In the current scenario, iOS 8.4.1 has patched all the jailbreak tools while iOS 8.4 can still be jailbroken.
Initially, it was possible to downgrade from iOS 8.4.1 as the signing windows for iOS 8.4 was still open. But unfortunately, Apple has stopped signing iOS 8.4, closing doors to all those coming back from iOS 8.4.1. It does not come as a surprise as Apple has been doing this for a few years now. Apple not only patches the jailbreak vulnerabilities via software updates, it also prevents users from going backward in software version.
TaiG jailbreak tool was able to jailbreak iOS 8.4, but it does not work on iOS 8.4.1 as Apple has patched several loopholes in its mobile operating system as has credited team TaiG for finding those vulnerabilities.
For a regular user, who does not care about jailbreak, there is nothing to be concerned about for them. But jailbreakers who are still rocking their iOS 8.4 jailbroken devices, must stay away from upgrading to iOS 8.4.1, or they will lose their jailbreak. Also be careful when installing a jailbreak tweak, as you may end up restoring your device to get rid of issues. Restoring means that you’ll have to upgrade to the latest iOS version, which is not jailbreak-able with any tool for now.