Unable to add an exception for HSTS turned out to have a really bad downside
I'm sitting here looking at a website that's supposed to have an auto-renewing Let's Encrypt certificate that expired yesterday; the site is serving with active HSTS and an expired cert.
The loss of the VPN software is critical; we need this to work expired certificate or not. (Yes I can tell the difference between an expired cert and a forgery.)
Maybe check this thread to see if there is something useful.
- /questions/1352563 Error code: sec_error_expired_issuer_certificate
Note that this might be harder to fix in an outdated Firefox version like 84.0 that you use.