My own grandma doesn't know what encryption/HTTP/TLS etc are. I think for those who are uninformed it's a sane default to not trust self-signed certs. That sai

My own grandma doesn't know what encryption/HTTP/TLS etc are. I think for those who are uninformed it's a sane default to not trust self-signed certs. That said, there should be a toggle in preferences or about:config to allow it for those who know what they are doing.