Microsoft's "Out of Band" Security Bulletin

Microsoft plans to issue an "out of band" patch today, e.g. a patch released on a day other than "Patch Tuesday". Microsoft Security Bulletin Advance Notification Thw defect, which hasn't been publicly described just yet, apparently exists in every version of Windows that anyone who is likely to patch anything actually uses:

• Windows 2000,
• Windows XP,
• Windows Server 2003,
• Windows Server 2008, and
• Windows Vista.

Microsoft describes this update as "critical" which means they know it can be remotely exploited without user intervention (and without exploit chaining, which they don't yet consider to be critical.)