Splunk Enterprise 6.6.x, when configured to run as root but drop privileges to a specific non-root account, allows local users to gain priv…

Splunk Enterprise 6.6.x, when configured to run as root but drop privileges to a specific non-root account, allows local users to gain privileges by leveraging access to that non-root account to modify $SPLUNK_HOME/etc/splunk-launch.conf and insert Trojan horse programs into $SPLUNK_HOME/bin, because the non-root setup instructions state that chown should be run across all of $SPLUNK_HOME to give non-root access.