A flaw was found in the Keycloak server's client management component. When a client is created or imported with authorization services enabled, the system fails to properly clear an internal session attribute used during the setup process. This allows an authenticated attacker with client management permissions to bypass security controls and upload a malicious JavaScript policy, which is then executed on the server when an authorization request is made. Successful exploitation could allow the attacker to run arbitrary code on the server, potentially compromising the entire system.