The CompSoc SSL Certificate Authority
The SSL certificate for HTTPS access to www.ox.compsoc.net is signed by a CA whose root certificate is installed in most browsers, and so accss to it should Just Work.
However, for SSL access to other CompSoc websites, and also for services like SMTP, IMAP and LDAP, we run our own certificate signing authority. If you want to trust this authority, you can download a copy of the root certificate, signed by the support team GPG key.