There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connection certificates and send their own.

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message

https://support.mozilla.org/en-US/kb/connection-untrusted-error-message

Websites don't load - troubleshoot and fix error messages

http://kb.mozillazine.org/Error_loading_websites

What do the security warning codes mean

Thanks for the reply but... not the issue. I should have been more specific about the problem. Alas, such are the non-sensical ramblings of a sleep deprived Linux newbie.  : (

My computer is running Ubuntu (20.04) linux. It was just recently set up and none of the security programs you mentioned are installed. In fact, once I got Ubuntu installed, getting Firefox (version 82) was my first priority (yeah, I like Firefox that much). So a real success story for me was to get Firefox working with the DOD Outlook Web Access (OWA). After much reading and sleuthing on the Internet, I was able to find the necessary pages to actually guide me to getting my DOD Common Access Card (CAC) working within Firefox. That is, until today when I received a notice there was an update available for Firefox. Immediately following the update, my CAC reader (an SCR3310) stopped working.

Did I mention I was sleep deprived? After taking a much needed nap, I sat down to try and figure out what happened. As a linux newbie, the log files did not make much sense to me so I carefully watched for physical signs/clues to the problem. And sure enough, the problem was quickly resolved after bringing up Firefox from a cold start.

When I had my CAC reader working correctly before, Firefox would prompt me for my CAC pin. With the new Firefox installed, I did not get that prompt. And when I visited the OWA site previously, I would notice the little green led flashing as the certificates on my CAC were presented to the site. With the new Firefox installed, I did not see that either, indicating a problem with the CAC software/middleware and/or Firefox.

In Firefox Preferences/Security & Privacy/Security Devices, I unloaded the CAC module and shut down Firefox. I then re-installed the CAC software (cackey_0.7.5-1_amd64.deb). Then it was time to reconfigure the security device again in the Preferences/Security & Privacy/Security Devices section. Viola! I was back in business.

So I'm not sure what in the Firefox update process killed the CAC, but removing the CAC module and re-installing it cleared the problem. Again, I thank you for your time in responding. It's the user community of Mozilla that makes "computering" more accessible to those of us newbies that want to understand more.

If anybody wants a detailed fix, let me know and I'll be happy to try to recreate/document the steps in detail. And for those of you that feel you'd like to help me out even further.... "A shiny new quarter..." (a line from the movie Christmas Vacation) to the person that can help me get the s/mime control installed so I can send and receive/read encrypted e-mails. Thanks much everybody!

David

That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems.