CVE-2026-63206: Zammad: Remote image tracking bypass via shortened URL scheme
Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, zammad's HTML sanitizer, which blocks remote images in ticket articles and email views, can be bypassed using a shortened URL format that omits the double slash after the scheme (for example a shortened HTTP URL instead of a shortened HTTP URL). Modern browsers treat both forms as equivalent remote URLs. As a result, an attacker who sends a crafted email or ticket can cause the recipient's browser to silently load an image from an external server, revealing when and by whom the ticket was opened. Zammad's "remote content blocked" warning is not shown because the sanitizer does not recognize the shortened form as remote. 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
Who can exploit this issue, and what interaction is required?
An attacker who can send a crafted email or create a ticket article can exploit it. The recipient must open the affected ticket or email view, causing their browser to load the attacker-controlled image.
What information can an attacker learn through exploitation?
The external image request can reveal that the content was opened and identify the recipient or viewer through request-related information available to the external server. The issue enables remote tracking despite the product's remote-content protections.
Will users see the normal remote-content warning?
No. The shortened URL form bypasses the sanitizer's remote-image recognition, so the "remote content blocked" warning is not shown.
Which versions need to be remediated?
Zammad versions prior to 7.1.2 are affected. Upgrade to version 7.1.2 to obtain the fix.