A doorhanger is a term for this sort of warning notification: <a href="http:&#x2F;&#x2F;i.imgur.com&#x2F;huWjWjq.png" rel="nofollow">http:&#x2F;&#x2F;i.imgur.com&#x2F;huWjWjq.png</a><p>As 6a68 mentioned, Firefox presents this doorhanger whenever any site other than addons.mozilla.org attempts to install an add-on.