Microsoft released an emergency security update on Sunday to address a certificate spoof issue. According to Microsoft Security Response Center,
We have discovered through our analysis that some components of the malware have been signed by certificates that allow software to appear as if it was produced by Microsoft. We identified that an older cryptography algorithm could be exploited and then be used to sign code as if it originated from Microsoft. Specifically, our Terminal Server Licensing Service, which allowed customers to authorize Remote Desktop services in their enterprise, used that older algorithm and provided certificates with the ability to sign code, thus permitting code to be signed as if it came from Microsoft.
The malware mentioned above is known as Flame, which is being used for targeted cyber espionage in Middle Eastern countries. According to estimates by Kaspersky in May 28, 2012, Flame had managed to infect about 1,000 computers, with victims including governmental organizations, educational institutions and private individuals.
The security update will be available through widows update service automatically. If you have disabled Windows Update, which you shouldn’t be doing whatsoever, you can still manually download and install it from this link.
This update is pretty much for all windows versions, including all server editions.
Check for more details on this Microsoft Knowledge Base Article, 2718704.