User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.4; en-GB; rv:1.9) Gecko/2008051202 Firefox/3.0 Build Identifier: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.4; en-GB; rv:1.9) Gecko/2008051202 Firefox/3.0 When I use an intercepting proxy, such as burp, I cannot add an exception to allow it's certificate to be valid. I get the following alert message: Alert login.yahoo.com:443 uses an invalid security certificate. The certificate is not trusted because it is self signed. The certificate is only valid for <a id="cert_domain_link" title="PortSwigger">PortSwigger</a>. (Error code: sec_error_untrusted_issuer) Then I click ok and I am on a blank page rather than the exception creation error page. If I try to add an exception manually through the encryption tab in advanced I get the same error message when I click the "Get Certificate" followed by the "Unable to obtain identification status for the given site". Reproducible: Always Steps to Reproduce: 1. Enbale proxy to localhost:8080 where burp (paras etc ....) is listening 2. Try to connect to any https site 3. Actual Results: Get Alert error message then a blank page Expected Results: Get and invalid SSL cert error page with the ability to add an exception The same thing happens on a new profile in this user account and on a new user account on the same box. Another mac user (same FF version - 3rc2 and OSX version - 10.4.11) here does not have this problem. If I visit a site with a self signed certificate without the intercepting proxy the exception addition page appears and functions as normal. I have tried reinstalling RC2 (and RC1), trying a new empty profile with no plugins and a new user account created on the box just for this purpose. While testing it did work correctly once but this was not reproducible in any manner.