The update also fixes a privilege escalation vulnerability that was reportedly also used in the web-based jailbreak.
The update applies to the iPhone 3GS and 4, iPod touch (3rd generation and later) and the iPad. The iOS 4.2.9 Software Update delivers the same fixes to the CDMA version of the iPhone 4.
iOS updates are currently available only via iTunes, which is inconvenient for those who are away from their computers. OTA (over the air) iOS updates are expected following the arrival of iOS 5.