CVE-2026-84463: Zammad: Stored HTML injection in Knowledge Base video widget enables forced session switching via unescaped iframe attribute
Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, a user with Knowledge Base editing rights for a category can embed a video widget in a published answer with a specially crafted value. When the answer is rendered, that value is inserted into the page's HTML without being escaped for its attribute context, allowing it to break out and inject additional HTML into the page. When another user who has permission to switch between user sessions views the affected answer, the injected HTML causes their browser to silently send a request to Zammad's session-switching endpoint using their own active credentials. This results in switching their session to an account chosen by the person who wrote the Knowledge Base answer. No action is required from the viewer beyond opening the published answer. This issue is fixed in version 7.1.2.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Zammadto a version that resolves this vulnerability.Fixed in 7.1.2
Event History
Frequently Asked Questions
Which users are realistically exposed to this issue?
The attack requires a user who can edit a Knowledge Base category to publish a crafted video widget. The affected viewer must open that published answer and have permission to switch between user sessions.
What does an attacker need to exploit the vulnerability?
An attacker needs Knowledge Base editing rights for a category and must publish an answer containing a video widget with a specially crafted value. They can choose the account to which an eligible viewer's session is switched.
Is viewer interaction required for exploitation?
No additional action is required after the viewer opens the affected published Knowledge Base answer. The browser sends the session-switching request using the viewer's active credentials.
How can I determine whether I am affected?
Zammad versions prior to 7.1.2 are affected. Review published Knowledge Base answers created or editable by potentially untrusted users, especially those containing video widgets, and identify users who have session-switching permission.
What should be done if patching is not immediately possible?
Restrict Knowledge Base category editing rights to trusted users and review or remove published Knowledge Base answers containing video widgets until the instance can be updated to 7.1.2.