It sucks to see the bad reviews. This add-on has been wonderful for me. I have had no problems logging in, other than forgetting my password. It has been improved as far as I can tell because it has been able to detect multiple credit card accounts and let you select which one it makes virtual cards for. You can easily manage your virtual cards from the link the add-on provides.

Someone said they did not like how you could only create virtual cards from the add-on while making a purchase. I think this is a good way to restrict creating these cards so that you only do so with an explicit purpose.

Anyway, great stuff. I wish Mozilla would say why they cannot label this as a recommended extension.