Apple has released iOS 4.3.5 for iPad, iPod touch, and GSM /AT&T iPhone 4 and iPhone 3GS, and iOS 4.2.10 for Verizon iPhone, which fixes a security vulnerability with certificate validation.
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. CVE-ID
Plug into iTunes and check for updates to get it. As always, if you’re Jailbroken already, stay away or you’ll lose your Jailbreak.