I still can make a test with Panopticlick to test it. Indeed, I succeed to install addons with the right-click method. Thank you.
But with all those warnings from Mozilla website, I have to admit this is not... very easy to think about this. Even the mouse pointer turns to forbidden link when you point on add to Firefox button. And this may be a prejudice for us when a new user install Trisquel as ABrowser is our default browser.
