Apple released a new version of QuickTime (7.1.5) which contains numerous bug fixes and a lot of important security patches. This article (http://docs.info.apple.com/article.html?artnum=305149) lists the security content of this release – you can see that it fixes 8 security vulnerabilities, all of which just require a user to click on a specially crafted file.

If you use QuickTime I would definitely recommend that you install the update as soon as possible as some of those security vulnerabilities look nasty.

Mac users can obtain it via the standard Software Update (Apple->Software Update..., reboot required) or, if you wish to install separately, you can find the Mac version at http://www.apple.com/quicktime/download/mac.html, while the Windows version can be downloaded from http://www.apple.com/quicktime/download/win.html.

UPDATE

We received couple of e-mails from people telling us that the built-in (auto) updater in older versions of QuickTime (still) doesn't find this new release. In other words, if you click on the "Update now" button, it will tell you that you have the latest version running.
So, at this point in time, if you want to run the latest (patched) version, you'll have to go there and download the installation file and install it manually.