This has happened before...fairly recently.
It used to be that traitors leaked classified info for money, sex, or some screwed up view of the world. Now we can add the need to win a technical argument on an online gaming forum...pathetic... This time it was a member of a French tank crew leaking performance data on the Leclerc S1 and S2. Apparently they actually posted classified documentation. Earlier this year, another gamer released info on the UK's Challenger 2 tank.
https://ukdefencejournal.org.uk/classified-tank-specs-leaked-on-war-thunder-game-forums-again/ (https://ukdefencejournal.org.uk/classified-tank-specs-leaked-on-war-thunder-game-forums-again/)
The War Thunder team is not at fault. They tried to stop it, and they definitely discouraged it. Still, the fact that Gaijin is a Russian company makes the situation even more uncomfortable.
Soon they will post data from self-conducted testing shooting.
Read about this yesterday. Didn't see if the person will be punished in any way.