Avoid permission "Access your data for all websites" if possible

As of review https://addons.mozilla.org/en-US/firefox/addon/css-reloader/reviews/1774328/:

> This app asks for a full acces to all your web datas (including saved logins and passwords !) why ? I don't think an app needs such a a critical acces to remove some cache (another authorisation exists for that in firefox).
That makes me very suspicious, and I didn't install this add-on.