This started failing a few months ago. Not sure if was from an update of Firefox or bad cookie. The pop-up to sign-in with browser launches a window comes up with another small window pops up and they both disappear. It is throwing an exception. I tried uninstalling and reinstalling and the same happens and couldn't complete the setup process. I did however discover a workaround to this. Go to a new Firefox browser window and sign into your Capital One account Then go back to the window you want to use a virtual account number for, select the Eno extension and it properly works. After I did this once, after logging out of Capital One. I tried again selecting the Eno externs and the sign-in with browser launches a pop-up window and allows me to sign-in

After reading the most recent reviews, I almost didn't install the extension. However, I figured, if I install it and it doesn't work, I'll just remove it. But, if I give it a try and it does work, I've gained a tool that will fit my needs.

I'm happy to say that I installed the extension and it does in fact work. I'm running Firefox 93.0 (64 bit) on a desktop computer that's only a year old with Windows 10 Home for an OS. I downloaded Eno ver. 3.6.1

I will admit, I can see why some may have had difficulties in using the extension. It seems to have an issue with signing in to a Capital One account directly from the Eno extension. However, here's what I found to work for me. I log in to my Capital One account first through the Capital One home page (as I would if I was going to check account transactions for example.) Once I'm signed in, I then click on the Eno extension icon in the upper right hand corner of the Firefox browser. Eno will usually recognize my account at that point. From there, I go to the merchant of choice, navigate to where I would enter my credit card info, click on the Eno icon if it's not already open, then click "Use". Eno guides me through creating a new virtual number like it's supposed to. No issues.

If my Captial One account times out on it's own, Eno is also logged out of my account. This is by design and keeps my account secure. However, attempting to log back in to Eno can be finicky. Here's 2 work-arounds that consistently work for me. Right-click on the Eno icon and select "Manage Extension." Disable Eno by clicking on the little toggle switch. Then re-enable. If that doesn't work, disable Eno again and close the browser. Now re-open browser. Log in to your Capital One account next before enabling Eno. After you're logged in, enable Eno from the Add-ons Manager in Firefox (if the Add-ons Manager tab is not already open, click on the "More" button which is 3 horizontal lines in the upper right corner, then click on "Add-ons and themes").

To reiterate, I have found these 3 basic procedures to be very helpful:
1. Sign in to your Capital One account first before attempting to use Eno.
2. Know how to disable and re-enable Eno. Use as needed.
3. Close browser and then re-start browser as needed.

I also noted that some reviewers expressed difficulty with the Eno extension slowing down internet browsing. I have not experienced that yet. However, disabling the extension can be done easily when it's not needed to speed things up if necessary.

I feel that this extension is worthwhile to try downloading and using. The extension is pretty intuitive. The settings are simple and clear. The extension will walk you through the process of creating a virtual card number in just a couple steps. Eno even automatically adds the card number in the appropriate field on some sites. If it doesn't add it automatically, just left-click the copy icon next to the virtual number and then right-click in the card number field on the merchant site and click "paste."

Another nice feature is that when you create a virtual card number, you can set a time limit on how long that number will be active.

I'm quite happy I took the leap and gave it a try. I don't always like to try new things as there's a learning curve and I often don't feel I have the time. However, dealing with a fraudulent charge on a credit card also takes time (this happened to me recently.) Since the virtual card feature has the potential to protect my main account and physical card number, the little bit of time it takes to use Eno is worth the time it saves in the long run.

Normally Eno works very well for me. It's a great tool! It somewhat frequently gets stuck on a loading screen when I use it and I have to refresh the page. Kind of annoying, but not a huge issue.

We don't like to give ANY info online

Confusing, confusing, confusing . . . until (after maybe 10-15 uses) the procedure begins to clear. This is a good, secure app, but NOT intuitive to use. Even after many uses, it confuses the heck out of me

I originally gave this a bad review and I almost sent the card back. But after 2 months, I have mostly changed my mind. I'm leaving my old review below, but here is a new perspective and 3 more stars, for 4 stars total.

I had no trouble installing this or using it many many times afterwards. It has worked, as far as I can tell, exactly as CapitalOne wants it to work. It was different from my Bank of America Shop Safe, so at first I hated it. But I have found a way to use it well. It has a drawback I will describe, but in some ways its also better. Here is how I use it.
1. Keep the extension disabled, except when you need a new virtual credit card number. That way it cannot spy on you at every website you go to. When you need one, enable it, get the virtual card number and record it in your password vault. Disable the extension. The only problem here is that you must have a website open to "attach" the virtual number to. I have been able to occasionally get a number that is not yet attached to a site, but I cannot repeat it. When I can, I will add that info here. But you are not actually limited to that website. You can even use the number over the phone. It appears that the number is permanently attached to the first credit processor that uses it, like ShopSafe was. This is very useful, because giving number over the phone to a human is much more dangerous than typing it into a computer. (CapitalOne - Please support getting numbers that are independent of a website!! Thanks!)

Your charge goes pending at first, so you cannot delete virtual card right away. But every time you get a new one, check for old ones that you can delete. This was my substitute for being able to define an expiration date in ShopSafe. Its not automatic, and you cannot set a maximum charge amount, but it seems good enough. That said, I decided I did not actually have to delete them every time. As long as I knew who I gave it to, if I got any bogus charges, I would know where the problem was. And since the number is probably locked to the first card processor that uses it, it is unlikely that it could be used by anyone who stole it in an IT breach from a company where I used it. I could probably have done this with ShopSafe too, but didnt realize it. Now I feel comfortable using it for recurring charges also.

So...I am pretty happy right now. If I stopped being able to use a number over the phone, I would probably go looking for another credit card to replace this. Using it over the phone is not officially supported and this is the main reason I only have it 4 stars. The other reason is that I have to enable and disable it every time I use it. But thats not too onerous. Thanks Capital One! Sorry for the misunderstanding at first....

*********** ORIGINAL REVIEW ***********
If you are looking for a ShopSafe replacement (recently cancelled by Bank of America) Eno based virtual credit card numbers from a CapitalOne card are not for you. These virtual credit card numbers do not give you the same protections from online fraud and do not work the way you would expect. First, you must use this app to create and manage virtual numbers. There is no website that I can find. This app is "always on" and watching your browsing activity to look for a site it thinks you might want a virtual credit card number for. So your browsing activity is no longer private. You cannot create a virtual card number until the app sees you on such a site. I was able to activate it on a dummy site, but then it links that URL to the credit card number. It set the expiration date of the virtual credit card 5 years into the future, oddly, past the expiration date for my real Capital One credit card. You cannot set a virtual number to expire after a certain number of months, like you could for ShopSafe numbers. Likewise, you cannot set a maximum charge amount for a virtual number, so anyone who gets this can charge as much as they like. So Eno virtual credit card numbers don't protect you from an unscrupulous online vendor, like ShopSafe did. In fact, if you read the Terms and Conditions, you will see that the virtual number may not even be locked to a specific merchant, like ShopSafe was. They appear to be testing this, but "...a VC# you create for use Merchant A should work at Merchant A, but may or may not work at Merchant B." So in my opinion, this does not really protect me very much. In fact, since there are no limits on the merchants and you cannot limit the maximum amount nor set a short expiration date, it may make you more vulnerable to fraud. If someone steals a virtual number from a company you gave it to, they can use it just as if they stole a card from your wallet. The only reasonable thing you can really do is delete the virtual number, but that assumes you know it was stolen. We usually dont find out about that until long long after it happens.

In fairness, unlike other reviews, I will say that I had no problems using my phone number to validate (via text messages) and get this set up. Setup worked just fine.

I am thinking carefully, because I really want a ShopSafe alternative, but this credit card will probably go back.

I hold two Capital One credit cards, and Eno does not allow me to change the default card. In the settings where this is supposed to be done, the card I want to designate as the default is grayed out, and a lock symbol appears to the right. I haven't locked the card myself, and I continue to use it for other purchases. Frustrating. What gives?