Apple has published an update for QuickTime, addressing several security flaws in the suite, some of which were particularly nasty. Version 7.4.5 fixes a total of 11 updates detailed in a security advisory that was published this week.
Several of the flaws were discovered at the TippingPoint Zero Day Initiative, lending some credence to the assumption that security conferences can actually help improve software. If you are using any version 7 release of QuickTime, it's highly suggested that you update.