as you probably know, there's a lot of media censorship of the "decadent capitalist influences" going on in Russia. The office responsible for such censorship is called Roskomnadzor - one of its functions is to "investigate potentially dangerous content".
According to a tweet on Roskomnadzor account, an investigation will be launched into the World of Tanks forums based on suspicions that they contain "illegal information".
What can that be we can only guess. Could also be an elaborate troll.. :)