Elasticsearch Service now supports the latest versions of the Elastic Stack, which includes Elasticsearch and Kibana 5.6.11 and 6.4.0.
From the Elasticsearch Service Console, you can upgrade your existing deployments to the latest versions of the Elastic Stack. To learn more about the best practices to use when upgrading, refer to Upgrade Versions.
For more information about the features in Elasticsearch and Kibana 5.6.11 and 6.4.0, refer to:
Service release: August 23, 2018