Apparently it adds a &quot;Complain&quot; tab to your browser when it detects offensive JavaScript: <a href="https:&#x2F;&#x2F;www.gnu.org&#x2F;software&#x2F;librejs&#x2F;manual&#x2F;librejs.html#Complaint-Feature" rel="nofollow">https:&#x2F;&#x2F;www.gnu.org&#x2F;software&#x2F;librejs&#x2F;manual&#x2F;librejs.html#Com...</a>