Revision Note: V1.1 (September 20, 2010): Revised Executive Summary to communicate that Microsoft is aware of limited, active attacks. Also added additional entries to the Frequently Asked Questions section and additional clarification to the workaround. Advisory Summary:Microsoft is investigating a new public report of a vulnerability in ASP.NET. An attacker who exploited this vulnerability could view data, such as the View State, which was encrypted by the target server, or read data from files on the target server, such as web.config. This would allow the attacker to tamper with the contents of the data. By sending back the altered contents to an affected server, the attacker could observe the error codes returned by the server. Microsoft is aware of limited, active attacks at this time.
More...
