The Group Policy Security Configuration policy implementation in Microsoft Windows Server 2003 SP2, Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8, Windows 8.1, Windows Server 2012 Gold and R2, and Windows RT Gold and 8.1 allows man-in-the-middle attackers to disable a signing requirement and trigger a revert-to-default action by spoofing domain-controller responses, aka "Group Policy Security Feature Bypass Vulnerability."