21
Firefox Has Quietly Integrated Brave's Adblock Engine
(itsfoss.com)
This is a most excellent place for technology news and articles.
From my unprofessional glance ar their repository, it uses a little, but not much. Take a look at their code; all or most of the filtering is done in JavaScript, the webassembly appears to be just ~~one~~ two modules. (It's in the "wasm" folder near the top of the list).
(Edit: I was looking at outdated code; the newer version uses more, but IMO pales in comparison to the JavaScript filtering logic)
Waterfox has a much smaller market share and much smaller budget, and was able to clear this with search partners just by promising not to block ads on them by default.