Search Guard Kibana Plugin versions before 5.6.8-7 and before 6.x.y-12 had an issue that an authenticated Kibana user could impersonate as kibanaserver user when providing wrong credentials when all of the following conditions a-c are true: a) Kibana is configured to use Single-Sign-On as authentication method, one of Kerberos, JWT, Proxy, Client certificate. b) The kibanaserver user is configured to use HTTP Basic as the authentication method. c) Search Guard is configured to use an SSO authentication domain and HTTP Basic at the same time