You can see in the screenshot that the certificate is issued for fb.mvfst.net and isn't valid for fbdelegatedcredentials.com.

Hello Mace2,

Would you please try this :

Type in the address bar about:config and press Enter. (promise to be careful, if asked)

Type in the search bar and look for the preference :

security.tls.enable_delegated_credentials

And make sure that its value is set to true

If you had to change the value, then close and restart Firefox.

I am using DOH and I am unable to get access to the site. I have set security.tls.enable_delegated_credentials to true and restarted but even if I did not I expect the site to be accessed.

Mace2 said

I am using DOH and I am unable to get access to the site. I have set security.tls.enable_delegated_credentials to true and restarted but even if I did not I expect the site to be accessed.

Bummer !

I just tried it, and after changing the value to true, I now get a blank page when I try to access fbdelegatedcredentials.com.

Just now I found this (scroll down to the comments at the bottom of the page):

https://www.thesslstore.com/blog/delegated-credentials-facebook-mozilla-cloudflares-new-tls-protocol-explained/

I don't know if this applies here though, but maybe worth a try (waiting, that is)  ?

See also:

• https://blog.mozilla.org/security/2019/11/01/validating-delegated-credentials-for-tls-in-firefox/

I think this site is faulty. Several networks identify this as not valid cert.

Mace2 said

I think this site is faulty. Several networks identify this as not valid cert.

If you have the value of that preference still set to "true"; would you try again please (if you haven't already, of course) ?

Unfortunately I can't try again, as I immediately after trying the first time, reset the value to "false".

It took that other user about 25 hours for it to work .....

McCoy said

I just tried it, and after changing the value to true, I now get a blank page when I try to access fbdelegatedcredentials.com.

My mistake : the reason I got a blank page is the fact that I had turned off "Enhanced Tracking Protection" for that site, to see what would happen.

I turned it back on and got the warning (same thing using Edge).

Changed the value of that preference to "true" again; now I got the warning with the "Advanced" button - clicked "Accept the Risk and Continue": blank page ..... :(

I'll try again about 25 hours from now.

I've tried other test sites ( with the value of the preference set to "true"), but none of them did what we expect them to do.

Then I realized that this will currently only work in Firefox Nightly or Beta:

https://dc.crypto.mozilla.org

This site does work "https://www.fbdelegatedcredentials.com/" run on firefox 70.01

the results are shown with security.tls.enable_delegated_credentials set true