Doesn't work: "Something went wrong" in both the add-on popup, and their setup page (capitalone.com/applications/eno/virtualnumbers/setup). Tried 5 times to sign in, with my username/password copied from the clipboard to make sure I didn't mistype anything. Also tried the Chrome extension - same failure.
GIVE ME A USEFUL ERROR! Not "Something went wrong". This is Error Management 101.
An it's not a "third party cookies problem". I made sure Firefox didn't block anything, and setup didn't work from CapitalOne's own setup page (no 3rd party situation there). This add-on is just broken.
Also, add-ons like these, that require permissions to READ AND CHANGE ALL THE DATA ON WEBSITES YOU VISIT, are a security nightmare. I worked at Google, and I can tell you there are easy ways to make extensions *request permissions on demand*, in a site-specific manner, instead of asking for that blank permission upfront, which most hapless users will automatically grant.
If this extension gets compromised (as quite a few others have), you're screwed. It will be able to read your bank/credit card/online Bitcoin wallet/ANY OTHER PASSWORD and data.
And it doesn't even work.
If you're looking for a simple and reliable alternative, sign up for Privacy.com. No spying extension to install - just generate card numbers from their website.
Advice for Capital One: you may think you're making it more convenient for customers to provide an add-on instead of a simple page to generate virtual CC #s from your own website (like Privacy.com does). Well, you're not. The more complicated a solution is, the higher the likelihood for it to fail.
If you really want to offer virtual card numbers for your customers, please do so in a simple, honest, transparent way - like Privacy.com. You have the advantage of the brand, cashback etc.