Oussama-Rahali

**Name of the Vulnerable Software and Affected Versions** pimcore/admin-ui-classic-bundle versions prior to 1.3.4 **Description** A potential security issue has been discovered in the `pimcore/admin-ui-classic-bundle`. The issue involves a Host Header Injection in the `invitationLinkAction` function of the UserController, specifically in the way `$loginUrl` trusts user input. The host header from incoming HTTP requests is used unsafely when generating URLs. An attacker can manipulate the HTTP host header in requests to the "/admin/user/invitationlink" endpoint, resulting in the generation of URLs with the attacker's domain. If a host header is injected in the POST request, the `$loginURL` parameter is constructed with this unvalidated host header. It is then used to send an invitation email to the provided user. This issue can be used to perform phishing attacks by making the URLs in the invitation links emails point to an attacker-controlled domain. **Recommendations** For versions prior to 1.3.4, update to version 1.3.4 or later to resolve the issue. As a temporary workaround, consider validating the host header and ensuring it matches the application's domain. It would also be beneficial to use a default trusted host or hostname if the incoming host header is not recognized or is absent. Restrict access to the `/admin/user/invitationlink` endpoint to minimize the risk of exploitation. Avoid using the `invitationLinkAction` function until the issue is resolved.