The second map pack for Call of Duty: Modern Warfare 2, the Resurgence map pack, was released for the Xbox 360 exclusively on June 3, 2010. It appears that a rock glitch had been found on the map, Fuel. Rob Bowling, Infinity Ward's Creative Strategist, posted on Twitter that "a fix for the rock exploit should be in the next patch."
The glitch in Fuel allows players to get inside of one of the rocks by repeatedly jumping at a certain angle, doing this glitch correctly allows players to be invisible to particular attacks, as well as allowing players to kill from within the rock.
No information as of yet has been release to whether or not Infinity Ward will patch the Playstation 3 and PC versions (I'm sure they will) of the Resurgence map pack when it is released on July 6, 2010.