Since you probably spent hundreds of hours on this, and they are apparently in violation of the license under which you contributed this work, maybe get a lawye

Since you probably spent hundreds of hours on this, and they are apparently in violation of the license under which you contributed this work, maybe get a lawyer and send them a letter asking for your attribution to be re-instated or removal of all the mis-attributed material? I mean Mozilla earns hundreds of millions a year and pays its CEO several millions a year, they could have well afforded to not violate your rights by spending a few dev days on writing a proper importer scripts.