This PowerPoint vulnerability is described at Microsoft Security Advisory #925984 http://www.microsoft.com/technet/security/advisory/925984.mspx
It appears that the vulnerability is due to errors when executing VB script SlideShowWindows.View.GotoNamedShow () automatically inside a PowerPoint presentation.
Information about the existence of related exploit code listed as NamedShows stack overwrite issue is public too. The author and origin of the exploit code is not currently known.
Microsoft is reportedly working on a fix and Security Bulletin Advance Notification Program reported about four upcoming October security bulletins affecting Microsoft Office recently.