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
Encore Mutation: Survival Versus

The following map fixes are part of an ongoing series of exploit fixes. These will appear on the Xbox 360 in a future update.

Swamp Fever: Swamp
Survivors can no longer bypass the airplane crescendo event.

Swamp Fever: Shanty Town
Survivors can no longer use a shanty roof to bypass a large section of the map

Swamp Fever: Plantation
Survivors can no longer bypass the first street by walking on top of a fence
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