According to the German government's IT security experts, a vulnerability found in iOS 4.3.3 that exploits the way the system handles PDF documents can allow for malicious software to be installed onto the device without the user's knowledge. Once successfully deployed, the malicious code can theoretically grant the attacker with root access to the system allowing them to read your messages, browse your contacts list, tinker with your camera, and pretty much do whatever they please with the device.
If this sounds like something that you have already heard before, you are not mistaken as a pretty similar flaw was found in iOS 1.1.1 about four years ago. The second major iOS release was not impenetrable either as an identical PDF vulnerability was present in it as well. Apple has yet to release a patch to fix the hole in iOS 4.3.3, but at this time, it seems like jailbreaking your device can fix the problem.
Fortunately, it has been reported that the security flaw has not caused any major damage so far, but despite that, it is advisable for you to be extra careful when browsing web sites that you do not trust. You do not want to be the first victim to make it on the list, now, do you?
source: German Federal Agency for Security in Information Technology via Gizmodo