In Firefox 4.x/5.x with a Server with a self signed certificate using IPv6 I can not add a "Security Exception" for this certificate. In Firefox 4.x/5.x I have a server ... it contains a self signed certificate. Using IPv6 I can not add a "Security Exception" for this certificate. 1. I log onto the server (using IPv6). I get the "Untrusted connection page" saying "This connection is Untrusted" 2. I click on "Add Exception.." under the "I understand the Risks" section. 3. The "Add Security Exception" dialog comes up. soon after the dialog comes up I get an additional "Alert" dialog saying An exception occured during connection to xxxxxxxxx. Peer's certificate issuer has been marked as not trusted by the User. (Error code sec_error_untrusted_issuer). Please note that this works in Firefox 3.6 (in IPv4 and IPv6). It also works in Firefox 4.x/5.x in IPv4 only IPv6 has an issue. What's wrong?