Well, but there are alternative extensions which do the same, clear cookies and all related datas from the websites when you leave them, except the whitelisted sites. I also used it before, but SiteBleacher is easier to handle

https://github.com/Cookie-AutoDelete/Cookie-AutoDelete

But in the Mozilla store read "About this Extension"

https://addons.mozilla.org/en-US/firefox/addon/cookie-autodelete/

There are also other FOSS extensions with a similar function.

https://karelkubicek.github.io/post/cookieblock

https://addons.mozilla.org/en-US/firefox/addon/forget_me_not/

https://github.com/JustOff/cookies-exterminator

Also some others, but they are proprietary soft.