Apple has just released iOS 4.3.4 for its range of iOS devices including the iPhone 4, iPad 2 and so on.
The latest version is minor in changes and only fixes a "security vulnerability" that allows Apple devices to be jailbroken using the malicious PDF trick.
iOS 4.3.4 Software Update
Fixes security vulnerability associated with viewing malicious PDF files.
Products compatible with this software update:
iPhone 4 (GSM model)
iPod touch (4th generation)
iPod touch (3rd generation)
For information on the security content of this update, please visit this website:
Plug in your device and get updating now!