Never thought of anti-crypto miner extensions, sounds shady. uBlock origin should do the trick, tho I would have expected pi-hole having most of those miners on it's block list by now. I think the service is coin-hive something, they changed their domain a lot to evade ban.

Seems like they released it as open source now: https://github.com/cazala/coin-hive, if that project is the javascript miner, it could be on any domain and very hard to block. Gonna have to dig deeper into that.