Keycloak: Arbitrary code execution via Stored Cross-Site Scripting (XSS) in organization selection login page

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.