[psychonic]

With that script above, your server will exit if anyone with "MasterRequestRestart" in their name joins. There are probably others ways to exploit it as well.

Instead, the SteamWorks extension has a hook for the callback from Steam that generates the actual message (although it does not work on all games), or any of the extensions that provide an HTTP API can query the Steam UpToDateCheck Web API with the server version from steam.inf to see if the server requires an update.