Kibana version 5.4.0 was affected by a Cross Site Scripting (XSS) bug in the Time Series Visual Builder. This bug could allow an attacker to obtain sensitive information from Kibana users.
https://www.elastic.co/community/security
https://www.elastic.co/blog/kibana-5-4-1-and-5-3-3-released
https://discuss.elastic.co/t/elastic-stack-5-4-1-and-5-3-3-security-updates/87952