Beginning in 2021, players of "War Thunder," a popular, free-to-play vehicular combat video game, have thrice posted classified documents related to three tanks of British, French, and Chinese origin, in an online forum dedicated to the game. The posting of the documents was reported first by UK Defence Journal, which wrote that one poster, who uploaded the manual to a British Challenger 2 tank, said he was motivated by a desire to get a "War Thunder" developer to make the tank more accurate in the game. Another poster, who claimed to be part of a French tank unit, uploaded a Leclerc S2 manual while engaged in an online debate about its turret rotation speed. The motivations of the user who posted allegedly classified information about China's DTC10-125 tank, and a piece of materiel, was not clear.

Classified details of the British Army's main battle tank, Challenger 2, have been leaked online after a player in a tank battle video game disputed its accuracy. The player, who claimed to have been a real life Challenger 2 tank commander and gunnery instructor, disputed the design of the tank in the popular combat video game "War Thunder", arguing it needed changing. He claimed game designers had failed to "model it properly". To support his argument the player posted pages from the official Challenger 2 Army Equipment Support Publication – a manual and maintenance guide. Excerpts from the documents, some of which were heavily redacted, appeared to show some documents had "UK RESTRICTED" label crossed out and a stamp of "UNCLASSIFIED" added, the website UK Defence Journal reported.