From release notes of 6.7.0p1: "Fixed security vulnerabilities in smtpd(8). Corrected an out-of-bounds read in smtpd allowing an attacker to inject arbitrary commands into the envelope file to be executed as root, and ensured privilege revocation in smtpctl(8) to prevent arbitrary commands from being run with the _smtpq group."
While adding a new ebuild, some consideration as to stabling again would be great (see bug 697704).
Also fixes https://github.com/OpenSMTPD/OpenSMTPD/commit/3cd16ecd7ae83a4ba093f5376f5c4ea229316790. Tree clean.