[wlesieutre]

The whole adtech industry is built around arbitrary javascript execution for tracking purposes, so we've also seen crypto mining scripts served through ad networks. For example: ads on YouTube mining Monero https://arstechnica.com/information-technology/2018/01/now-e...

This is being used by anybody who can sneak a javaascipt into your page or an iFrame that you embed, which has become too easy to do. When it comes down to it, IMO, site owners are responsible for what ads and scripts they allow to be served via their page, but I think I'm in the minority on that opinion.

Ad networks (the more reputable ones anyway) are playing a cat and mouse game of allowing a Turing complete js environment and trying to prevent its use for doing particular pieces of math. I'm glad Firefox is joining in as well, but I'd be happier if we didn't have this problem to begin with.