Open Ticket Request System (OTRS) 4.0.x before 4.0.28, 5.0.x before 5.0.26, and 6.0.x before 6.0.3, when cookie support is disabled, might allow remote attackers to hijack web sessions and consequently gain privileges via a crafted email.
https://www.otrs.com/security-advisory-2017-10-security-update-otrs-framework/
https://www.debian.org/security/2017/dsa-4069
https://lists.debian.org/debian-lts-announce/2017/12/msg00018.html
https://github.com/OTRS/otrs/commit/720c73fbf53e476ca7dfdf2ae1d4d3d2aad2b953
https://github.com/OTRS/otrs/commit/36e3be99cfe8a9e09afa1b75fdc39f3e28f561fc
https://github.com/OTRS/otrs/commit/26707eaaa791648e6c7ad6aeaa27efd70e7c66eb