Kibana versions prior to 5.6.1 had a cross-site scripting (XSS) vulnerability in Timelion that could allow an attacker to obtain sensitive information from or perform destructive actions on behalf of other Kibana users.
An error was found in the X-Pack Security TLS trust manager for versions 5.0.0 to 5.5.1. If reloading the trust material fails the trust manager will be replaced with an instance that trusts all certificates. This could allow any node using any certificate to join a cluster. The proper behavior in this instance is for the TLS trust manager to deny all certificates.