An error was found in the permission model used by X-Pack Alerting 5.0.0 to 5.6.0 whereby users mapped to certain built-in roles could create a watch that results in that user gaining elevated privileges.

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.

Elasticsearch X-Pack Security versions 5.0.0 to 5.4.3, when enabled, can result in the Elasticsearch _nodes API leaking sensitive configuration information, such as the paths and passphrases of SSL keys that were configured as part of an authentication realm. This could allow an authenticated Elasticsearch user to improperly view these details.

X-Pack Security 5.2.x would allow access to more fields than the user should have seen if the field level security rules used a mix of grant and exclude rules when merging multiple rules with field level security rules for the same index.

Elastic X-Pack Security versions 5.0.0 to 5.4.0 contain a privilege escalation bug in the run_as functionality. This bug prevents transitioning into the specified user specified in a run_as request. If a role has been created using a template that contains the _user properties, the behavior of run_as will be incorrect. Additionally if the run_as user specified does not exist, the transition will not happen.