An identified security vulnerability in Windows XP could enable an attacker to compromise a user's Windows-based computer and gain complete control over it, if the user visited the attacker's web site or took other, less likely, actions. You can help protect your computer from this and other identified security concerns by installing this update. Who should read this bulletin: Customers using Microsoft ® Windows ® XP Impact of vulnerability: Run code of an attacker's choice Maximum Severity Rating: Critical Recommendation: Customers using Microsoft Windows XP should apply the patch immediately. Affected Software: Windows XP Home Edition Windows XP Professional Windows XP Tablet PC Edition Windows XP Media Center Edition Download the update.
I wouldn't rely on the Win Update site, quite a few times a patch has been available through TechNet for a while before it's added to the Win Update site. Besides what fun are automatically downloading patches when you can look through the thousands of TechNet entries to get the latest updates .