Apple's Safari on Windows Platform Threat
Microsoft is investigating new public reports of a blended threat that allows remote code execution on all supported versions of Windows XP and Windows Vista when Apple’s Safari for Windows has been installed. Safari is not installed with Windows XP or Windows Vista by default; it must be installed independently or through the Apple Software Update application. Customers running Safari on Windows should review this advisory.
More information: Microsoft Security Advisory (953818) and MSRC's blog: Security Advisory 953818 Posted.