I think you may be referring to Certificate Patrol (https://addons.mozilla.org/en-US/firefox/addon/certificate-patrol/ https://addons.mozilla.org/en-US/firefox/

I think you may be referring to Certificate Patrol (https://addons.mozilla.org/en-US/firefox/addon/certificate-patrol/ https://addons.mozilla.org/en-US/firefox/addon/certificate-p...)