Revision Note: V1.0 (May 14, 2013): Advisory published.
Summary: Microsoft is releasing this security advisory to help ensure customers are aware that an update to the Microsoft Malware Protection Engine also addresses a security vulnerability reported to Microsoft. The update addresses a vulnerability that could allow remote code execution if the Microsoft Malware Protection Engine scans a specially crafted file. An attacker who successfully exploited this vulnerability could execute arbitrary code in the security context of the LocalSystem account and take complete control of the system.
via Latest Security Advisories http://technet.microsoft.com/en-us/security/advisory/2846338