If your a Windows user, there is another hole in the web that you need to guard against. Apple is no longer issuing updates to QuickTime on the Microsoft platform. This coupled along with the that the Department Homeland Security has reported potential flaws should definitely throw up a red flag.
The recommended best practice in this case is to remove/uninstall Apple QuickTime from your PC at your earliest convenience. After doing so, it is highly recommended to update all other software including all anti-virus products. Regular system updates should also be made.
Source: The Verge