Interesting tidbit: a few years back I encountered a Minecraft server with a dynamic map on a website. After checking it out for about 5 minutes I noticed some weird CPU usage so I asked the server admins.
They apparently to came to an agreement with the players where, to support the server, a browser miner would be ran on the dynamic map website.
spent a good part of my morning trying to figure out why Reddit was down but nobody on the internet mentioned that. Tried chrome and Reddit is fine, so something weird must be going on with FF