We're preparing an update for all three S.T.A.L.K.E.R. games.
This update resolves a recently found vulnerability in the network game client code, which allows intruder to crash the game using specially created server and map names.
Thanks to the fan community sites stalker-life.ru and team-stalker.ucoz.com and also personally ufa and Sin! for help in discovering and addressing the threat.
After the upgrade, user maps must follow naming convention, namely starting with "mp_".
Update is already live on STEAM, standalone Multi-Patch v.2 for retail versions will be released today.