Related to WEBDAV and the Anonymous account (IUSER_<>)

Microsoft is investigating new public reports of a possible vulnerability in Microsoft Internet Information Services (IIS). An elevation of privilege vulnerability exists in the way that the WebDAV extension for IIS handles HTTP requests. An attacker could exploit this vulnerability by creating a specially crafted anonymous HTTP request to gain access to a location that typically requires authentication.

We are not aware of attacks that are trying to use this vulnerability or of customer impact at this time. Microsoft is investigating the public reports.

http://www.microsoft.com/technet/security/advisory/971492.mspx