All Elasticsearch versions from 1.0.0 to 1.5.2 are vulnerable to an attack that uses Elasticsearch to modify files read and executed by certain other applications. Upstream bug/commit unknown at the time of writing.

Mitigation: =========== Users should upgrade to 1.6.0. Alternately, ensure that other applications are not present on the system, or that Elasticsearch cannot write into areas where these applications would read.

External References:

https://www.elastic.co/community/security/