The iPhone Dev Team, a well-known group of iPhone hackers, first discovered the change in an unlocked developer's version of iOS 5, which is expected to be released this fall.
Normally, to restore your iPhone to an earlier version, you'd save "SHSH blobs" (which are like digital signatures to authenticate software) at a specific timestamp and use a third-party app to restore your firmware back to that time. The SHSH blobs are static and can be used as often as you like.
But the team found that in iOS 5, Apple has prevented people from being able to save these blobs for a specific timestamp. Instead, Apple will re-assign your phone a new SHSH blob each time your reboot your device in jailbreak mode, making saved blobs irrelevant since Apple can just reject ones that were saved.
Looks like Eric Sadun over at TUAW has found that the new Apple TV is definitely hackable, as the device is instantly recognizable by PhoneView (an OS X app that let’s you browse the disk of your iOS devices.) Since the Apple TV runs iOS and has been found to pack 8GB of storage, aside from the fact that the Apple TV version os iOS has already been hacked by the iOS Dev-Team using their SHAtter jailbreak, it’s a no-brainer that we will be seeing third-party apps on this thing at some point in the very near future.
Read More | TUAW