Apple has released the latest update to iOS, now version 4.3.5, to address security flaws. This update comes quickly after the 4.3.4 update which addressed a similar security flaw used to jailbreak iDevices. Users should download the update via iTunes when their iPhone, iPad, or iPod touch is plugged into their computer.
From the Apple knowledge base article about the update:
"Available for: iOS 3.0 through 4.3.4 for iPhone 3GS and iPhone 4 (GSM), iOS 3.1 through 4.3.4 for iPod touch (3rd generation) and later, iOS 3.2 through 4.3.4 for iPad.
Impact: An attacker with a privileged network position may capture or modify data in sessions protected by SSL/TLS.
Description: A certificate chain validation issue existed in the handling of X.509 certificates. An attacker with a privileged network position may capture or modify data in sessions protected by SSL/TLS. Other attacks involving X.509 certificate validation may also be possible. This issue is addressed through improved validation of X.509 certificate chains."