(I do not work for Mozilla so this is speculation):<p>As far as I can tell, side loaded extensions require a full, non-automated, review <a href="http:&#x2F;&#x2F;i.imgur.com&#x2F;r070Grv.png" rel="nofollow">http:&#x2F;&#x2F;i.imgur.com&#x2F;r070Grv.png</a> and it wouldn&#x27;t surprise me if side-loaded extensions were the worst offenders.<p>Upon discovering a malicious extension, Mozilla could look through all extensions they&#x27;ve signed and blacklist (<a href="https:&#x2F;&#x2F;addons.mozilla.org&#x2F;en-US&#x2F;firefox&#x2F;blocked&#x2F;" rel="nofollow">https:&#x2F;&#x2F;addons.mozilla.org&#x2F;en-US&#x2F;firefox&#x2F;blocked&#x2F;</a>) all extensions with a similar signature similar to how some anti-malware databases work.<p>There is probably not all that much stopping you from writing a malicious extension that passes the AMO automated review (example: <a href="https:&#x2F;&#x2F;addons.mozilla.org&#x2F;en-US&#x2F;firefox&#x2F;blocked&#x2F;i1058" rel="nofollow">https:&#x2F;&#x2F;addons.mozilla.org&#x2F;en-US&#x2F;firefox&#x2F;blocked&#x2F;i1058</a>), but the cost for malware writers is going to be significantly higher since it will be far easier for Mozilla to shut them down via their blacklists.