Apple has released a software update to their iOS, iOS 4.3.4 considering the jailbreak issues. The recent update is available for iPhone 3GS, iPhone 4, iPod Touch 3G, iPod Touch 4G and all the iPads.
iOS 4.3.4 Software Update
Fixes security vulnerability associated with viewing malicious PDF files.
Also there is a software update iOS 4.2.9 for the CDMA iPhone 4. iOS 4.3.4 build number is 8K2, while iOS 4.2.9 is 8E501