Yesterday Microsoft released an “out of band” security advisory (one that is considered of such imminent importance that it’s released outside of the regular monthly “Patch Tuesday” schedule). Advisory 2718704 pertains to attacks that use unauthorized digital certificates that are issued by a Microsoft Certification Authority. The problem affects all currently supported released Microsoft Windows operating systems, from XP to Windows 7 and including all Windows Server 2003 and 2008 editions. Also affected are mobile devices, including Windows Mobile 6.x, Windows Phone 7 and 7.5. Windows 8 Consumer Preview and Release Preview are also affected and should be updated.
Find out more here:
http://technet.microsoft.com/en-us/security/advisory/2718704