Apple issued a QuickTime update today that addresses a number of security vulnerabilities in the media player and its Web plug-in. This update is only for Windows-based machines that have QuickTime installed, since Mac systems have had this update applied in recent security updates for OS X.
Apple's QuickTime media player and plug-in are used by about half of all Windows PCs and all of Apple's systems since OS X includes QuickTime as a core component of the OS. Because of its popularity, attackers may use vulnerabilities in it as a vector for compromising the system on which it is installed.