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

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.

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.

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.