Skype&#x27;s &quot;Click to Call&quot; add-on is a good (bad?) example of the harm caused by &quot;side-loaded&quot; add-ons. It causes Firefox to crash, hang, or take multiple seconds to respond to mouse clicks. The add-on is quietly injected into Firefox by Skype&#x27;s application installer and can&#x27;t be disabled or uninstalled from Firefox&#x27;s Add-on Manager. Users must uninstall it from the Windows&#x27; &quot;Add&#x2F;Remove Programs&quot; Control Panel.<p><a href="https:&#x2F;&#x2F;bugzilla.mozilla.org&#x2F;show_bug.cgi?id=1215970" rel="nofollow">https:&#x2F;&#x2F;bugzilla.mozilla.org&#x2F;show_bug.cgi?id=1215970</a>