An issue was discovered in Citadel through webcit-926. Meddler-in-the-middle attackers can pipeline commands after POP3 STLS, IMAP STARTTLS, or SMTP STARTTLS commands, injecting cleartext commands into an encrypted user session. This can lead to credential disclosure.
http://uncensored.citadel.org/msg/4576039
http://uncensored.citadel.org/dotgoto?room=Citadel%20Security