There are new vulnerabilities that have come out for Quicktime that Apple will not patch. This means that Quicktime is no longer safe to use. The best solution is to uninstall Quicktime and use something else to play your videos. Here are some instructions on how to uninstall Quicktime.

Windows 7:
Left click on the Start Menu and choose Control Panel.
If the view is set to Category mode, left click Uninstall a program under the Programs section.
If the view is set to Small or Large Icons mode, left click Programs and Features.
Scroll through the list of programs until you find Quicktime.
Right click on the Quicktime entry and left click Uninstall.
Left click Yes when it asks if you are sure you want to uninstall Quicktime. (you may get several prompts asking if you want to remove or uninstall)

Windows 8.1 & 10:
Right click on the Start Menu and choose Control Panel.
If the view is set to Category mode, left click Uninstall a program under the Programs section.
If the view is set to Small or Large Icons mode, left click Programs and Features.
Scroll through the list of programs until you find Quicktime.
Right click on the Quicktime entry and left click Uninstall.
Left click Yes when it asks if you are sure you want to uninstall Quicktime. (you may get several prompts asking if you want to remove or uninstall)

For a Quicktime alternative, I recommend VLC Player which you can download here:

http://www.videolan.org/vlc/download-windows.html

SOURCE: Trend Micro