In Open Ticket Request System (OTRS) through 3.3.20, 4 through 4.0.26, 5 through 5.0.24, and 6 through 6.0.1, an attacker who is logged in as a customer can use the ticket search form to disclose internal article information of their customer tickets.
https://www.debian.org/security/2017/dsa-4066
https://lists.debian.org/debian-lts-announce/2017/12/msg00015.html