> The CAB is only concerned with the WebPKI. This means HTTPS.

[citation needed]

The title of their current (2.2.2) standard is "Baseline Requirements for the Issuance and Management of Publicly‐Trusted TLS Server Certificates":

* https://cabforum.org/working-groups/server/baseline-requirem...

§1.3, "PKI Participants", states:

> The CA/Browser Forum is a voluntary organization of Certification Authorities and suppliers of Internet browser and other relying‐party software applications.

IMHO "other relying-party software applications" can include XMPP servers (also perhaps SMTP, IMAP, FTPS, NNTP, etc).