Insufficient privilege verification in Zammad v5.3.0 allows an authenticated attacker to perform changes on the tags of their customer tickets using the Zammad API. This is now corrected in v5.3.1 so that only agents with write permissions may change ticket tags.

An issue in the component /api/v1/mentions of Zammad v5.3.0 allows authenticated attackers with agent permissions to view information about tickets they are not authorized to see.

A vulnerability in Zammad v5.3.0 allows attackers to execute arbitrary code or escalate privileges via a crafted message sent to the server.