It seems that a vulnerability in Direct X’s Direct Show subsystem is coming under attack. Now the vulnerability allows execution of code, but only as the logged on user, which means if you are smart, then the normal user account does not have admin rights, and code executed through this vulnerability won’t be able to do as much.
The thing that makes this so major, even though it doesn’t automatically grant admin rights, is the fact that Direct X is used for a lot of multimedia applications. In fact most games use either Direct X or Open GL for rendering. Now add on that the issue is with a Quicktime subroutine in Direct Show, and that even if you have Quicktime installed on your system, the Direct X exploit Can still be access, and you have the makings of a huge issue.
Now the other thing that is interesting is that this only affects Windows 2000, 2003 and XP. Vista and 2008 are not affected, or at least have not been shown to be affected by this vulnerability.
Workarounds and more information is available in the actual Microsoft Security Advisory for this vulnerability.