Zammad: HTML sanitizer API path allowlist bypass via interior path traversal in img src/srcset

Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, attacker-controlled HTML in inbound emails or tickets could bypass the image URL sanitizer using path traversal sequences. When an authenticated agent views the content, the browser resolves the URL to a protected API endpoint and sends the request with the agent's session cookie, enabling side effects such as forced logout without any user interaction. This issue is fixed in version 7.1.2.