Apple’s recently released iOS 6.0 beta 1 also brings a fix for the loop holes present in iOS 5.0.x which allowed the iPhone Dev Team to develop a downgrade method for A5 devices (iPad 2, iPad 3 and iPhone 4S).
The method which was first released in Redsn0w 0.9.11 b1 involves two steps. First it upgrades the device to latest iOS build and then downgrade it to previous version. However, in this method the modem firmware (baseband) doesn’t downgrade.
At the release time of A5 downgrade method, MuscleNerd told us that this hack could be fixed anytime by a simple firmware update. But fortunately Apple didn’t fix it in any iOS 5 firmware updates.
Now a fix in iOS 6 beta 1 means that any user who updates his device to iOS 6 final build won’t be able to downgrade it to any previous version. As the singing windows for iOS 5.1.1 is still open, so it means the iOS 6 beta 1 users can downgrade anytime to iOS 5.1.1.
On the other hand this iOS 6 downgrade fix won’t affect the A4 devices due to bootrom level exploit “Limera1n”. The users having iPhone 4, iPhone 3GS and iPod Touch 4G will be able to downgrade iOS 6.0 to iOS 5.1.1 or any previous firmware version.
So, the users who have A5 devices and who can’t live without jailbreak must not install the public iOS 6 build on their devices until iPhone Dev Team releases a tethered or untethered jailbreak for iOS 6.0 on iPad 3, iPhone 4s and iPad 2.