Comment by everforward

Isn't there standard text on these? On a cover page and/or headers/footers?

I get that the content of the documents is not known, but I would think the structure of them is known and could be matched on. Perhaps specific phrases that are only likely to appear in military documents, or a classification level in a header/footer, or even some specific combination of font, font weight, line spacing and indentation.

They could maybe even slurp up the text from PDF's they blocked to prevent someone from posting similar plaintext. Probably not, though, because an endpoint that says whether something is or isn't classified is basically a classified document generator with enough time or clever tricks.

Then just forward the reports to whatever country's military owns those docs (or let the company's government do that). I think War Thunder only needs to make a nominal effort; the various militaries of the world will take care of backing it up with a dire threat.