Microsoft has said it is releasing an emergency patch for its Windows XP, Windows 2000 and Windows Server 2003 operating systems today. The patch is rated as critical and it being released as an out-of-cycle patch. Normally Microsoft releases its patches on the second Tuesday of each month, but with little information to go on, researchers are concerned that the flaw may be serious and is being actively exploited by hackers. The last time Microsoft released a fix prior to the normal release date was in April 2007. The patch should be available at 10:00 AM PST.