Information
This setting controls whether Firefox will or will not automatically fill in the URL text box and auto-fetch the certificate on behalf of the user. When Firefox encounters an invalid certificate and the user clicks 'Add Exception', a dialog is displayed with a text box to fetch the certificate from the given URL.
Rationale:
Requiring the user to manually enter the server's URL and fetch the certificate may provide additional opportunity to scrutinize the certificate before adding an exception for a potentially fraudulent certificate.
Impact:
Setting this configuration to 0 forces the user to enter a URL and click the 'Get Certificate' button before adding an exception for an invalid cert.
Solution
To establish the recommended configuration, set browser.ssl_override_behavior to 0:
Type about:config in the address bar
Type browser.ssl_override_behavior in the filter
Ensure the setting is set as prescribed.
OR
Open the mozilla.cfg file in the installation directory with a text editor
Add the following lines to mozilla.cfg:
lockPref('browser.ssl_override_behavior', 0);
Default Value:
2