Logstash Insertion of Sensitive Information into Log File

An issue was identified by Elastic whereby sensitive information is recorded in Logstash logs under specific circumstances.

The prerequisites for the manifestation of this issue are:

* Logstash is configured to log in JSON format https://www.elastic.co/guide/en/logstash/current/running-logstash-command-line.html , which is not the default logging format.

* Sensitive data is stored in the Logstash keystore and referenced as a variable in Logstash configuration.