Please read carefully and check if the version of your Zammad system is affected by this vulnerability. Please send information regarding vulnerabilities in Zammad to: security at zammad.com
An attacker with the permissions of a Ticket customer can access internal information about it's own account, the Ticket history and related Tickets. It's also possible for the unauthorized user to access the recent Tickets, merge Tickets and split Ticket functionality that should be only accessible for agent Users.
This vulnerability is fixed in the latest versions of Zammad and it is recommended to upgrade to one of these.
Fixed releases can be found at:
Or just update your Zammad if installed via OS package manager.
Online version of this advisory: https://zammad.com/news/security-advisory-zaa-2020-13
Send all remarks to security issues to security @ zammad.com.