There's an update for QuickTime available. Version 7.3 fixes several flaws that malicious sites could use to install unwanted software (arbitrary code execution) just by viewing a specially crafted image or movie file.
Mac as well as Windows versions of QuickTime should be updated. If you're a Windows users and don't have iTunes/Apple Software Update installed, click here.
And then there's a Microsoft Security Advisory regarding a vulnerability in Macrovision's secdrv.sys driver. The driver comes installed on Windows XP and Windows Server 2003. This vulnerability could allow an elevation of privileges.
Macrovision has a driver update which will likely be included in Microsoft's monthly updates.