QuickTime 7.3.1 Security Update
Apple has released QuickTime 7.3.1, which addresses a number of security issues. The release is available for Windows, Leopard (10.5), Tiger (10.4), and Panther (10.3) and available in your software update.
This update is recommended for all QuickTime 7 users and addresses a widely publicized security flaw in QuickTime revealed by Symantec. Details of this and other security fixes are listed in this support document.