Apple has released updates for its iOS devices to fix the recently discovered vulnerability that allows remote jailbreak without user intervention. The gravity of this flaw was such that Apple rushed out the fixes, which resolve two issues:
Viewing a PDF document with maliciously crafted embedded fonts may allow arbitrary code execution
Malicious code running as the user may gain system privileges
More information is available from Apple's Security Updates page.
These updates affect the iPhone and iPod touch running iOS 4.0 or later, and the iPad, running iOS 3.2 or later. The updates are only available through iTunes, when the devices are connected to a computer.