Also, this is enough to sue, isn't it?
From the Mozilla Add-Ons FAQ @ https://addons.mozilla.org/en-US/firefox/faq
Are add-ons safe to install?
Unless clearly marked otherwise, add-ons available from this gallery have been checked and approved by Mozilla's team of editors and are safe to install. We recommend that you only install approved add-ons. If you wish to install unapproved add-ons or add-ons from third-party websites, use caution as these add-ons may harm your computer or violate your privacy. Learn more about our approval process
This add-on was marked otherwise. (Well, according to the claims above.)
You can definitely argue that having unvetted add-ons on the site at all is bad, but your particular point isn't relevant.