A Reddit user recently notified the popular online game League of Legends that cryptocurrency mining malware was running on their servers.

League of Legends, owned by Riot Games, is a billion dollar plus revenue generating game. When Reddit user Lestergonzaga came across the malware on their system, he made them aware by posting in the subreddit dedicated to the game.

The malware, using Coinhive’s Javascript miner, was taking advantage of players’ gameplay to mine the privacy cryptocurrency Monero. The affected League of Legends server was located in the Phillippines.

Once Lestergonzaga posted his findings, many other players expressed their concerns as well. The use of their computers to mine cryptocurrency during gameplay could greatly affect their computer’s performance. Being that League of Legends is a multiplayer online battle arena (MOBA), where two teams are pitted against each other in a battle royale environment, it’s a game that is taken very seriously by most players.

When League of Legends became aware of the issue, they took swift action. They found the affected code on July 9, posting the following message to their Facebook page: “There was an unauthorized modification of the League of Legends PH client lobby where a certain javascript code was inserted. This code performs blockchain mining on affected computers, which consumes CPU resources from these computers. Apart from increased CPU usage, extensive analysis from our security engineers has determined that there is no other impact on affected computers.”

Two days later, on July 11, they were able to remove the code: “Our security engineers have removed this javascript code and ensure that all users, including those who were previously affected, will no longer encounter this issue. We treat security matters with utmost priority and sincerely apologize for this incident, and for the inconvenience you have experienced.”

Exact numbers on the amount of Monero mined through the game is unknown. As stated above, League of Legends generates more than a billion dollars annually, so the sheer amount of gameplay may have mined large amounts of the cryptocurrency.