Ingo H3 is a generic frontend for editing Sieve, procmail, maildrop and IMAP filter rules.
Ingo H3 fails to properly escape shell metacharacters in procmail rules.
A remote authenticated attacker could craft a malicious rule which could lead to the execution of arbitrary shell commands on the server.
Don't use procmail with Ingo H3.
All Ingo H3 users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=www-apps/horde-ingo-1.1.2"