Downgrade to iOS 8.1 (or upgrade, for that matter) is no longer possible. Two weeks after the release of iOS 8.1.1, Apple has stopped signing the previous version. The move comes as no surprise, as the company has been known to stop signing IPSW files just days after a new release.
Those seeking to install or restore iOS 8.1 will have to use iOS 8.1.1 instead. The news comes hot on the heels of an iOS 8.1.1 jailbreak solution released by TaiG team. Despite the 8.1 signing window closing, users looking to jailbreak their iOS devices can use the TaiG jailbreak tool to jailbreak iOS 8.1.1.
The Pangu jailbreak is rendered obsolete, except for devices which are already running iOS 8.1. In any case, with TaiG available it makes more sense to update to iOS 8.1.1 before jailbreaking. While TaiG team claims to have an iOS 8.2 jailbreak waiting in the wings, it's possible that when Apple releases iOS 8.2 they will patch the jailbreak.
Pangu team was credited by Apple in three security patches released with iOS 8.1.1, which broke the Pangu jailbreak tool.
Impact: A local user may be able to execute unsigned code
CVE-2014-4455 : @PanguTeam
Impact: A malicious application may be able to execute arbitrary code with system privileges
CVE-2014-4461 : @PanguTeam
Impact: A malicious application may be able to launch arbitrary binaries on a trusted device
CVE-2014-4457 : @PanguTeam
Newest iPhone FAQs
iOS 8.2 beta has already been seeded to developers. Expect a public release early next year. In the meantime, iOS 8.1.1 is the latest and only firmware available for newer iOS devices.