A flaw was found in Keycloak, specifically in the organization selection login page. A remote attacker with manage-realm or manage-organizations administrative privileges can exploit a Stored Cross-Site Scripting (XSS) vulnerability. This flaw occurs because the organization.alias is placed into an inline JavaScript onclick handler, allowing a crafted JavaScript payload to execute in a user's browser when they view the login page. Successful exploitation enables arbitrary JavaScript execution, potentially leading to session theft, unauthorized account actions, or further attacks against users of the affected realm.
Restrict access to the Keycloak administration console and login pages to trusted networks only, ideally through a VPN or by configuring firewall rules. Furthermore, ensure that only highly trusted administrators are granted manage-realm or manage-organizations privileges within Keycloak. Regularly review and audit administrative accounts and their assigned roles to minimize the risk of unauthorized access and exploitation. If the Keycloak service is restarted or reloaded, these network and access restrictions will persist.