Hátőőő...
https://www.cacert.org/index.php?id=1
A kapcsolat nem biztonságos.
...
www.cacert.org uses an invalid security certificate.
Persze van megoldás a FAQ-ban:
http://wiki.cacert.org/FAQ/BrowserClients#Mozilla_Firefox
"New versions of Firefox (as version 39.0 on Linux Ubuntu 14.10) don't permit importing of the CAcert Root cert (root.crt, root.der) as its signing algorithm MD5 is treated as obsolete and not secure. Simply use the add-on stated above."
Nem érzem, hogy ezzel előrébb lennénk. :)