Apple updated their iOS from 4.3.3 yesterday.

That’s because last week, the German government discovered some security holes in Mobile Safari related to PDFs. Today, Apple issued a few updates to fix the problem (one for most iOS devices, and one for the Verizon iPhone). Just head into iTunes, plug in your device, and hit "Check for Updates" to grab them.

“the patch comes in two versions, thanks to the different flavors of the iPhone 4. iOS 4.3.4 applies to the iPad and iPad 2, the third- and fourth-generation iPod touch, the iPhone 3GS, and the iPhone 4 (GSM model); users of the CDMA model of the iPhone 4 instead get iOS 4.2.9.” – Computerworld

However, if you're jailbroken, you won't want to update just yet, since this update will remove the jailbreak from your iPhone.

As I reported in the past, jailbroken phones are less secure. That is because they can use non “store bought” apps which can be malware infected.

This method of exploitation (through Freetype Truetype font 1) occurs through the Apple CoreGraphics Framework to execute malicious code which allows the code to gain system privileges by posing as the user.

Source: http://www.computerworld.com/s/article/9218449/Apple_releases_iOS_updates_to_fix_PDF_vulnerabilities