For those of you having issues with the recent file uploading exploit, there is a patch, however it has only been released to the client. If you want to update your server then you need to copy engine.dll from Steam\steamapps<steamname>\garrysmod\bin to <server path>\orangebox\bin.
This is only temporary till Valve adds the fix to the HldsUpdateTool.
You may also want to backup your original engine.dll just incase this solution has any side-effects (although we didn’t find any).
Good sentence: http://www.facepunch.com/showpost.php?p=17246913&postcount=434 (Teddi Orange)