Microsoft is aware of nine fraudulent digital certificates issued by Comodo, a certification authority present in the Trusted Root Certification Authorities Store, on all supported releases of Microsoft Windows, Windows Mobile 6.x, Windows Phone 7, Microsoft Kin, and Zune devices. Comodo advised Microsoft on March 16, 2011 that nine certificates had been signed on behalf of a third party without sufficiently validating its identity.

These certificates may be used to spoof content, perform phishing attacks, or perform man-in-the-middle attacks against all Web browser users including users of Internet Explorer.

These certificates affect the following Web properties:

• login.live.com
• mail.google.com
Google
• login.yahoo.com (3 certificates)
• login.skype.com
• addons.mozilla.org
• "Global Trustee"

Comodo has revoked these certificates, and they are listed in Comodo’s current Certificate Revocation List (CRL). In addition, browsers which have enabled the Online Certificate Status Protocol (OCSP) will interactively validate these certificates and block them from being used.

An update to help address this issue is available for all supported releases of Windows and is beginning to be delivered to Windows Phone 7 customers.

Details: Microsoft Security Advisory (2524375): Fraudulent Digital Certificates Could Allow Spoofing