This is completely false. Firefox extensions have access to everything the browser does and can contain arbitrary native code. There's a reason Mozilla's addo

This is completely false. Firefox extensions have access to everything the browser does and can contain arbitrary native code. There's a reason Mozilla's addon repository has a review process. What makes addons better than ActiveX controls is that they're understood to extend the browser for the user's benefit, not merely make a crappy website work. Fewer people would buy that a bank website needs to install a Firefox extension before you can log in.