Apple dropped official support for QuickTime on Windows at the end of last week, that means no more updates for Windows users. Its been the mainstay of much cross platform video compatibility, specifically for embedded media playback via web pages. It is also used by some DAWs as part of the libraries required to access video and audio codecs. Its also part of some Bootcamp installations - installing Apple tools to ensure Windows can talk to your Apple hardware if running a dual boot system.
At the same time as this announcement, the US Government issued a warning that there are two Zero-Day exploits detected using loopholes in the Quicktime Libraries for Windows. Zero Day exploits are vulnerabilities identified by hackers that before the vendor (in this case Apple) can fixe them. And as they have no intention of fixing it due to dropping support...
If you don't need it, it is recommended (by Apple and the Feds) that you uninstall from your Windows PC.
US government alert: