Microsoft has released an advance notification bulletin for September 2010 to announce an out of cycle (not on the normal Patch Tuesday) security update that is detailed in KB Article 2416728.
This was the ASP.net vulnerability that was made public this past month and a work around was originally provided.
A security update will be released on 28 September 2010 to patch this issue on all Windows systems.
They will also host a webcast to discuss this update on the same day:
Microsoft will host a webcast to address customer questions on the out-of-band bulletin on September 28, 2010, at 1:00 PM Pacific Time (US & Canada). Register now for the September 28, 1:00 PM webcast. Afterwards, this webcast is available on-demand. For more information, see Microsoft Security Bulletin Summaries and Webcasts.