https://gitflic.ru/project/magnolia1234/bypass-paywalls-firefox-clean
And for anyone concerned about it being hosted in Russia I will quote my own research from several months ago. Original comment follows:
Magnolia's Twitter Account: [ Removed in Accordance with Instance Rules ]
Nitter Link: https://nitter.tiekoetter.com/Magnolia1234B
Wikipedia: https://en.wikipedia.org/wiki/Bypass_Paywalls_Clean
It used to be on the official Firefox Extensions repository until DMCA takedown notices made them take it down.
It used to be on gitlab until DMCA takedown notices made them take it down.
It used to be on github until DMCA takedown notices made them take it down.
It moved to gitflic.ru not because it's sketchy, but because of copyright enforcement.
It's kind of like sci-hub, in a way, it can only actually survive in a country that doesn't respect the US copyright cabal.
That being said, I've never audited the code, but it's open source (MIT-license) and signed by Mozilla as noted on its gitflic page:
PS although the add-on was removed from Mozilla’s add-on store (AMO) (because of DMCA Takedown Notice) it’s still signed and manually checked for security by Mozilla (hence the delay in signing).