Still skimming the paper, but the JS attack appears to be processor-intensive (please chime in if you interpret it differently!). Any widespread, indiscriminate use of such an attack in the wild seems like it would eventually be detected as surely as client-side cryptocurrency mining was discovered. If you aren't a valuable target, if you don't visit sites that are shady enough to discreetly mine bitcoin in your browser, and if you use an adblocker to defang rogue advertisers, then you probably shouldn't lose too much sleep over this (which is not intended to diminish how awesome (in the biblical sense) this attack is).

That said, if there were ever a time to consider installing NoScript, now's it: https://addons.mozilla.org/en-US/firefox/addon/noscript/