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.

Zammad 5.3.x (Fixed 5.4.0) is vulnerable to Incorrect Access Control. An authenticated attacker could gain information about linked accounts of users involved in their tickets using the Zammad API.

Zammad 5.3.x (Fixed in 5.4.0) is vulnerable to Incorrect Access Control. An authenticated attacker with agent and customer roles could perform unauthorized changes on articles where they only have customer permissions.

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.