On November 20, 2007, Infinity Ward released a patch to upgrade the game to version 1.2. The patch addressed a glitch reported by several community members which allowed players to see through walls when in a left vertical lean. It also prepared files for compatibility with the future release of the Call of Duty 4: Modern Warfare Mod Tools.
Patches and Fixes: Call of Duty 4: Modern Warfare v1.2 Patch - Demo Movie Patch Download Section - GamersHell.com
Call of Duty 4: Modern Warfare v1.2 Patch - gameupdates.org
Call of Duty 4: Modern Warfare v1.2 Patch for PC Download at GameSpot
Call of Duty 4: Modern Warfare v1.2 Patch - FileFront.com