OpenSMTPd -- Local information disclosure

Qualys reports:

We discovered a minor vulnerability in OpenSMTPD, OpenBSD’s mail server:
an unprivileged local attacker can read the first line of an arbitrary
file (for example, root’s password hash in /etc/master.passwd) or the
entire contents of another user’s file (if this file and
/var/spool/smtpd/ are on the same filesystem).