The Department of Homeland Security’s United States Computer Emergency Readiness Team (US-CERT) has issued an alert recommending that
Apple’s QuickTime program should be uninstalled from all Windows computers. Security vulnerabilites were found, but Apple will no longer be providing security updates for this product.

More information is at: https://www.us-cert.gov/ncas/alerts/TA16-105A.

Instructions on how to uninstall QuickTime can be found on Apple’s website: https://support.apple.com/en-us/HT205771.