If I were a bit more paranoid, I'd think it was part of a plan out of Cupertino. Luckily, it seems hard to exploit, if the hacker that discovered it right.

Researcher Finds New Flaw in QuickTime for Windows - PC World

In a video with a thumping techno beat, Petkov shows a QuickTime file sitting on the desktop of a PC running XP SP2. If a user opens the malicious file, Petkov then has control of the PC, demonstrated by the way the applications Paint, Calculator and Notepad are seen launching, apparently without further user intervention. The demonstration is repeated on a PC running Windows Vista inside a virtual machine.
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