CipherFox displays the current SSL/TLS cipher and certificate chain in the Add-on bar and Site Identification dialog.
The Qualys SSL Labs Server Test for the current domain is also accessible from the menu.
You can click CipherFox to show a popup menu with the certificate chain. Clicking on any certificate shows you its detailed properties. Variables are available in the Preferences window to customize the output.
Earlier versions were released under the MPL 1.1.
CipherFox is distributed by AMO: https://addons.mozilla.org/en-US/firefox/addon/cipherfox/