This addon is great. Blocks all popups and it allows you to whitelist. I got it specifically to block the popups that just won't stop on certain shady websites that allow you to view movies or shows etc and it works perfectly.
Popup Blocker Ultimate blocks almost all popups that other pop up blockers fail to stop. And the dev is honest and does not sell our usage data or other dubious practices. I seriously recommend to support this guy with a donation, honest behavior and good quality should be rewarded!
And for the love of god, those of you that whine about the page that asks for a donation: that page should not show more than once when you install and once when you uninstall. However I have noticed that it may also appear after updating Firefox. But in any case ffs, stop whining! This pop up blocker is super awesome, it works really well, it's FREE, and the devs does not sell our browsing habits or usage data or other such nonsense.