LambdaGeneration earlier broke the news that the Dota 2 Client had been Leaked with references to actual HL2: Episode 3 Code which has recently been verified by Steam user barneyinblue:

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dota 2 beta/bin/dota_staging_latest_good.TXT

dota/staging/game/bin/ep3.fgd
dota/staging/src/game/client/client_ep3.vpc

dota/staging/src/game/server/ep3/blob_mine.cpp
dota/staging/src/game/server/ep3/blob_regenerator.cpp
dota/staging/src/game/server/ep3/dust_cloud.cpp
dota/staging/src/game/server/ep3/gas_pump.cpp
dota/staging/src/game/server/ep3/npc_advisor_roaming.cpp
dota/staging/src/game/server/ep3/npc_advisor_roaming.h
dota/staging/src/game/server/ep3/npc_advisor_roaming_spit.cpp
dota/staging/src/game/server/ep3/npc_blob.cpp
dota/staging/src/game/server/ep3/npc_blob.h
dota/staging/src/game/server/ep3/npc_blob_tiny.cpp
dota/staging/src/game/server/ep3/npc_blob_tiny.h
dota/staging/src/game/server/ep3/npc_composite_companion.cpp
dota/staging/src/game/server/ep3/shape_target.cpp
dota/staging/src/game/server/ep3/weapon_egon.cpp
dota/staging/src/game/server/ep3/weapon_flamethrower.cpp
dota/staging/src/game/server/ep3/weapon_flamethrower.h
dota/staging/src/game/server/ep3/weapon_flechettegun.cpp
dota/staging/src/game/server/ep3/weapon_gauss.cpp
dota/staging/src/game/server/ep3/weapon_icegun.cpp
dota/staging/src/game/server/ep3/weapon_pipebomblauncher.cpp
dota/staging/src/game/server/ep3/weapon_teleport.cpp
dota/staging/src/game/server/ep3/weapon_weaponizer.cpp
dota/staging/src/game/server/ep3/weaponizer_concrete.cpp
dota/staging/src/game/server/ep3/weaponizer_liquid.cpp
dota/staging/src/game/server/ep3/weaponizer_metal.cpp

dota/staging/src/game/client/ep3/fx_gauss.cpp
dota/staging/src/game/client/ep3/splatter.cpp

[dota 2 beta/bin/dota_staging_debug_latest_good.TXT]

dota/staging/src/game/shared/ep3/blob_shareddefs.h
dota/staging/src/game/shared/ep3/npc_advisor_roaming_shareddefs.h
dota/staging/src/game/shared/ep3/weaponizer_shared.h

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If these environmental type weapons are indeed now part of the Half Life universe, the future looks very interesting for one Gordon Freeman.

For more on the DOTA 2 leak checkout the original teamliquid forum thread which is subtlety restrained considering the nature of the leak.