Apple thinks you should uninstall Quicktime for Windows as soon as possible.

There are 2 reasons.  

1) Apple is no longer going to be releasing any updates for this product for Windows

2) There are apparently 2 new vulnerabilities that Apple deemed critical enough that they released 2 advisories for recently.  

Those advisories would be ZDI-16-241 which allows remote attackers to execute code through Quicktime and ZDI-16-242 which essentially allows the same kind of vulnerability. None of this applies if you are running if you are running Apple OSX.  But if you have a Windows PC you might as well just go ahead and uninstall the program.  

Keeping your computer up to date and running a good Anti-virus software is the best way to avoid malware and or vulnerability for attack.