If you like your iOS 4.3.3 Jailbreakme 3.0 jailbreak, you may not want to hit that Update button when iTunes prompts you to update to iOS 4.3.4.
Comex used a PDF exploit hole in iOS 4.3.3 and earlier to offer the easiest jailbreak ever through jailbreakme.com. But, unlike other jailbreak tools this is a userland exploit which means it can be easily fixed by an iOS update.
Apple has been quick to close that hole and released a patched iOS version 4.3.4 today.
Of course, this is an exploit that can be maliciously used by others outside the usually benevolent jailbreak community. So, if you stay with your iOS 4.3.3 jailbreakme jailbreak on your iPhone or iPad, then there is a way to close this exploit without updating to iOS 4.3.4.
PDF Patcher 2 is a Cydia tweak that Comex has released which basically closes this hole for everyone else. Just install this from Cydia and you don’t have worry about updating to iOS 4.3.4. If you mistakenly updated your iPhone or iPad to iOS 4.3.4, there are ways to downgrade iOS 4.3.4 to iOS 4.3.3.
If you are not jailbroken on your iPhone or iPad, then you should immediately update to iOS 4.3.4.
