Apple had released its latest iOS 4.3.4 which is available for iPhone, iPod Touch and iPad devices. 

Apple's iOS 4.3.4 is simply a minor security update which fixes a vulnerability associated with software's PDF viewing. The vulnerability is reported to allow hackers to gain full control of Apple's device hence users are encouraged to download the new iOS 4.3.4, unless of course, you are using applications such as Jailbreakme.

Sources: PCgameshardware, CNet, Securitynewsdaily