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: Follow The Liter
Added support custom campaign particles. Custom campaigns can specify their own particles_manifest.txt file as well as any per map files. The per map files need to reside in the maps directory and be in the form: <mapname>_particles.txt
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