Firefox 68 user here. Leechblock rating reduced to 3 stars; stops working, does not block URLs reliably. This used to be a stable and VERY useful extension, but now (Sep 2019) it stops working altogethter every few weeks (fails to block any of my specified URLs). Removing the extension and re-installing sometimes fixes the issue, but only temporarily. Hopefully a future extension or Firefox update will fix the bug causing LeechBlock to suddenly stop working entirely.