return the button to ignore SEC_ERROR_BAD_SIGNATURE

This is old stuff but maybe help focus

https://support.mozilla.org/en-US/questions/1206972

https://support.mozilla.org/en-US/questions/1206972 https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can didn't help

For example, I had a problem with the website https://pt-start.ptsecurity.com/. OperaGX works with it without any problems.

You can override expired cert, you can override self–signed cert.

You can't override connections that can't be established/decrypted (bad signature, handshake, wrong fields, cipher suite agreement et al.) because, well, they come in either as gibberish or non–secure data wrapped in secure channel ending up filling wrong bits — and yes you can't override industry–guaranteed sets of standards (namely HSTS or explicit revocations) even while the connection would technically be possible — but it does not conform to what the site operator or issuer mandates.

While I can't say too much about other browsers' certificate trust checks, this one seems revoked by the issuer about three days ago certificate.revocationcheck.com/pt-start.ptsecurity.com and the site operator should have rotated that or replaced with some ACME/certbot–provided fresh ones that are easy to replace.

Notably, the site works over insecure connection as well, so just change the protocol to http:// explicitly and you can open it.