Revision Note: V1.0 (December 10, 2013): Advisory published.
Summary: Microsoft is announcing the availability of an update for Windows 8 and Windows Server 2012 that revokes the digital signatures for nine private, third-party UEFI (Unified Extensible Firmware Interface) modules that could be loaded during UEFI Secure Boot. When the update is applied, the affected UEFI modules will no longer be trusted and will no longer load on systems where UEFI Secure Boot is enabled. The affected UEFI modules consist of specific Microsoft-signed modules that are either not in compliance with our certification program or their authors have requested that the packages be revoked. At the time of this release, these UEFI modules are not known to be available publicly.
via Latest Security Advisories http://technet.microsoft.com/en-us/security/advisory/2871690