It’s possible to legally cheat in Call of Duty: Modern Warfare by simply bypassing a shader download.
On Nov. 12, Moden Warfare was updated in one of the largest patches since the game's release. Like all other patches for PC, players have to download shader updates each time. But one player skipped these downloads and was granted a wallhack.
This doesn't apply to all textures in the game, though. The player can be seen running through a fully-textured house but the roof is entirely transparent. The player could see an enemy running toward him because the floor textures are see-through.
This bug likely occurs due to an issue with rendering. An error with the textures could result in a non-rendered wall or placement. A type of wallhack may allow players to see through certain textures due to this issue.
If players don't want to exploit this bug, it can be fixed manually. Players need to restart the game and install the shaders. Since this bug is unintended and the player isn't using a hack, a ban is unlikely.
Modern Warfare players are rightfully disappointed that this feature can be exploited in the game. Some have even suggested that the option shouldn't be downloadable. Instead, they should simply be implemented as a part of the update.
But since this bug is game-breaking, fans can expect it to be patched soon.