This happened with Monster Hunter World's Iceborne expansion. It updated the included version of Denuvo and added many, many threads that constantly scanned the

This happened with Monster Hunter World's Iceborne expansion. It updated the included version of Denuvo and added many, many threads that constantly scanned the game executable for modifications as an anti-cheat mechanic. A modder distributed a tool to bypass the anti-cheat and restore performance the same day the expansion released. It took over two weeks for Capcom to get the game playable again, and many more before they improved performance back to roughly pre-update levels. For reference, I'd been using Steam Proton to play the base game on Linux and was getting 60fps at nearly max settings. After the update, I got 1. One frame per second. I saw a number of similar reports from native Windows players.