World of Tanks player who watches match replays from Wargaming's free-to-play arena battler? You'd best be careful, as the company has publicized a vulnerability that allows third parties to "inject malicious code into replay files."
The problem will be addressed in WoT's 9.5 update as well as the 1.7 patch for World of Warplanes. In the meantime, Wargaming says that "the code is executed automatically when opening the compromised replays via the game client. Your system may be at risk if you download potentially modified replays from the internet."