On my corporate intranet, there are a couple of internal systems with web interfaces that generate the sec_error_reused_issuer_and_serial error. Every resource on mozilla.org and other sites that I have found lists only two options: 1. get the admin of the site to fix the problem, or 2. temporarily add an exception Even the Mozilla support article specifically about this error message is not helpful: https://support.mozilla.org/en-US/kb/Certificate%20contains%20the%20same%20serial%20number%20as%20another%20certificate I have asked the exact same question here and the question was closed without an answer as well: https://support.mozilla.org/en-US/questions/996094 Nowhere have I been able to find information regarding a permanent exception. I understand that ideally, for a public website, the long term fix will be for the website admin to fix the problem, however there must be a way to permanently add an exception in Firefox to completely ignore this error message. I already tried deleting the "cert8.db" file and this has not resolved the problem. I am not interested in any temporary exceptions or temporary resolutions; I am specifically asking how to permanently ignore this error message. Thanks.