I had the same issue and tried removing the
xpack.security.enabled: false setting. However, then kibana failed to complete startup; serving "Kibana server is not ready yet" with nothing in the logs.
Then when I put the config back and restarted kibana again, elasticsearch (on the same server) was OOM killed. Having resolved that, Kibana still didn't work, and making another request appears to have DoSed the whole machine (whether through CPU load or OOM or both I'm not yet sure). After a reboot it all seems to be working again (though the original issue remains).
So in summary, I had the same (minor) problem, and trying the suggested fix made it considerably worse.