To fix the PDF vulnerability which has been used by Comex in JailbreakMe 3.0 to jailbreak iPhone, iPod Touch, iPad and iPad 2, now Apple has dropped iOS 4.3.4 update for iDevices.
Note: Owners of unlocked or jailbroken iDevices must stay away from iOS 4.3.4 update.
Download iOS 4.3.4 for iPhone
Download iOS 4.3.4 for iPod Touch
Download iOS 4.3.4 for iPad