PROBLEM:
2 critical new flaws were found in Apple’s Quicktime video player. While Apple knows about these 2 new bugs it  is no longer issuing security updates for Quicktime for Windows. This warning does not apply to Apple’s Quicktime on Mac systems. It is not known why Apple is still patching Quicktime for MAC systems but not for Windows systems.
The bugs can be used to attack a PC if a user visits a compromised web page or opens an infected file.
RECOMMENDATION:
Uninstall Quicktime on Windows systems.
More info here: