How to bypass the "secure connection failed" warning in Firefox 33

Open Firefox's about:config

Set security.tls.insecure_fallback_hosts = www.domain.com (substitute the domain you're having the problem with)

Reload the page

This problem has been reported to Mozilla in their support forum.

The reason is that Firefox 33 has fully switched to the more strict libPKIX and you can no longer disable this library and fall back to the previous NSS code.

See related Mozilla blog post and bug:

Bug 975229 - Remove NSS-based certificate verification

It appears that they will not change this behavior.

If your problem is like mine, on a webmin site, try recreating the certificate from inside webmin. It helped me get back the "make security exception" in FF 33.0!

I had the same issue with Webmin and firefox 33. When I looked at the SSL certificate that Webmin was using, I found that it was using a 512 bit key! This must have been the default key size when I installed Webmin a couple of years ago.

Firefox 33 no longer supports keys less than 1024 bits (with good reason). See site compatibility

You can fix this right from Webmin if you use another browser that lets you bypass this type of error or if you temporarily disable SSL in webmin by setting ssl=0 in /etc/webmin/miniserv.conf and restart webmin with "/etc/init.d/webmin restart". Just login to the Webmin web UI and select: Webmin -> Webmin Configuration -> SSL Encryption -> Self Signed Certificate. Fill in the form (or leave the defaults) and then click the Create Now button. If you temporarily disabled ssl enable it with ssl=1 in /etc/webmin/miniserv.conf and restart webmin with "/etc/init.d/webmin restart". This will update your self-signed certificate for Webmin and you will now be able to access the page from Firefox 33 (With the usual browser warning about an untrusted connection).