Update: Let me just start with my latest review of this extension- it's mostly broken. Not sure if it's simply related to FIrefox updates, but this extension rarely works these days. It's much more trouble than it's worth. I can no longer recommend its use.

Sadly, there is no other way (that I know of) to generate virtual card numbers without using the extension. So, that means the virtual cards feature is generally not available now.

It's disturbing that a company like Capital One would allow one of their financial products/services to be so unreliable.

Old review:
As usual, reviews are all love or hate (1 star or 5 star). Such absolutism (all-or-nothing think) is rarely useful to anyone. So, first, throw out all of the 1's and 5's and dig deeper into the reviews that have actual thoughtful analysis of the product.

In this particular experience, the Capital One add-on, Eno, is wonderfully useful... when it works. For me, a frequent online shopper, it provides two things I value highly: convenience and security. I love having it available at shopping sites, with all the info I need to complete the purchase. I don't have to look up my card info and manually fill it in. Very nice.

Sadly, some updates to Firefox and a few sites' code break the add-on. But I've found this to be true of many of the add-ons I use. Anytime an app or an operating system pushes out an update, it's not uncommon for software that interacts with it to break or have issues. So, this is not a particular sin of this add-on. It applies to many add-ons.

Most importantly, I love Eno and the feature from Capital One to use a virtual number. The add-on just makes it easier to use. One can still interact with the Capital One website to manage their virtual numbers. Due, once again to occasional breaks from browser updates or particular sites, I have had to get creative when using the feature. This can be frustrating.

It's not perfect, but overall, it works more than it doesn't, and the ability to generate a one-time use number is invaluable when it comes to online security. Keep in mind, the virtual number feature is very flexible. You can keep using the number for that particular site, but lock it, so it's only usable when you allow it, you can just delete it, or leave it unlocked for one particular merchant only (e.g. for a subscription).

If you're not using a virtual number, you are asking to be hacked. Get this add-on, take a deep breath when it breaks from time to time, and feel a whole lot better when you use your credit card online.