According to this http://blog.dob.sk/2014/07/23/firefox-31-self-signed-certificate-sec_error_ca_cert_invalid/ http://blog.dob.sk/2014/07/23/firefox-31-self-sign

According to this http://blog.dob.sk/2014/07/23/firefox-31-self-signed-certificate-sec_error_ca_cert_invalid/ http://blog.dob.sk/2014/07/23/firefox-31-self-signed-certifi... it's a 3+ month old bug in Firefox's certificate verification code. I used to be able to access my router's control panel in Firefox (and other sites with self-signed certs), and still can in other browsers (albeit after jumping through the usual hoops), the sites are not at fault here. I'm just an average user that no one cares about, but if you dare read the comments on that blog, it seems this bug and the slow response to it pissed off a lot of corporate IT folk whose self-signed apps they borked.