Core/Handlers: Prevent possible movement hijacking exploit, original code by VladimirMangos

--HG--
branch : trunk

src/server/game/Server/Protocol/Handlers/MovementHandler.cpp

@@ -278,6 +278,10 @@ void WorldSession::HandleMovementOpcodes(WorldPacket & recv_data)
     /*    return;
     }*/
 
+    // prevent tampered movement data
+    if (guid != mover->GetGUID())
+        return;
+
     if (!movementInfo.pos.IsPositionValid())
     {
         recv_data.rpos(recv_data.wpos());                   // prevent warnings spam