Installing update KB2850851 on Windows 8 Pro introduces a drop in performance with Call of Duty 4 and Call of Duty World at War, while the game is open and moving the mouse in game, csrss.exe CPU usage will raise significantly and introduce a framerate drop during mouse movement inside the game. Uninstalling the update fixes this.
In my case, the issue seems to only appear with Roccat Kone XTD mouse (and possibly other high end gaming mice, but I don't have the resources to confirm that), but not with an inexpensive Logitech B110 or Apple MacBook Pro's trackpad. So far I have tried it on my Desktop PC and a MacBook Pro, both running Windows 8 Pro.