Apple has released QuickTime 7.6 which can be downloaded and installed via QuickTime software update preferences, or from Apple Downloads.

This release contains numerous security updates. For details of security fixes and installation details see

http://support.apple.com/kb/HT3403

QuickTime 7.6 for Windows can be downloaded from

http://support.apple.com/downloads/QuickTime_7_6_for_Windows

select the option with or without iTunes as appropriate.