Updates to Left 4 Dead 2 have been released. The updates will be applied automatically when your Steam client is restarted. The major changes include:

Left 4 Dead 2
Community Mutation: Special Delivery
Added protection against servers executing restricted commands on clients
Fixed clients sometimes not getting disconnected from the server after getting a consistency error
Fixed an exploit that could cause players to fall through the elevator in No Mercy
Fixed the still-crownable witch in Realism Versus
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