I installed this addon because I was annoyed by a popup and Firefox on Android is not able to block pop-ups. This addon works and disables the popup. There is no convenient way to manage settings for sites, so if you (accidentally) allow or block pop-ups permanently you have to clear all site settings in Firefox in order to revert the setting.
Edit in response to dev: Thank you for the fast reply even if the reviews is not the right place. Clearing site data did help me. I updated my review. (And please be a little less insulting on people who don't give 5 stars, have 4 for a really good addon, 5 if you improve the settings)
I was using a very popular competitor popup blocker and began having problems with it blocking form elements as well as privacy concerns. I tried Popup Blocker Ultimate and am very pleased with its performance.
It is very easy to whitelist sites that you want to enable popups. Very Effective lightweight popup blocker. Highly Reccomended