Works Really Well. Maybe Too Well Puntuado con 2 de 5 estrellas

Installed the extension. It wiped every cookie I had immediately, including ones I wished to keep, upon installation, which didn't allow me to setup the whitelist I didn't need until I installed the extension.Now I can't set up the whitelist because I don't know the site addresses of all of those cookies, including a whole lot of do-not-track cookies.This extension -- which doesn't require a restart -- really needs a permission to begin its work before it starts, which means it needs a persistent setup to initialize it. Or at least a warning about how it will behave upon installation.

Without the surprise, wholesale cookies destruction, my star rating would be much, much higher. Right now, 2 stars will have to do. I'm feel more like 1.5, and the .5 would be me being kind.

Esta valoración es de una versión anterior del complemento (0.3.3.1-signed). 

Sorry about your bad initial experience. Automatically removing cookies is what this add-on is all about. Could I have described the actual behaviour more clearly so you would not have been surpised? English is not my native language; I'm open to suggestions.
Mozilla will not greenlight add-ons that open a modal message when they are loaded like you propose. Opening the warning in a background tab would make no sense, because the cookies would be long gone after you've read it.