Unknown Unauthorized login

I have numerous Tasmota devices installed in my house. I was referring to my system log and I received this error:

21-04-20 09:06:58 INFO (MainThread) [supervisor.auth] Auth request from 'core_mosquitto' for 'mqttuser'
21-04-20 09:06:59 WARNING (MainThread) [supervisor.auth] Unauthorized login for 'mqttuser'

My question is 2 fold. How do I detect what Ip this is coming from? The log doesn’t provide sufficent detail. Can I use a backlog command to update all mqtt devices in the house with the correct password or does this require the device to be it to be logged in in the first place?

Look in the Mosquitto log. It should list the client id.

Perfect. Found it. I was looking under the MQTT log which was blank.

So I understand about MQTT more clearly, does the device need to be logged in to be able to send commands to it? Was that my only way to fix the issue?

Basically, yes.

You publish commands to topics on the broker and if any device is subscribed to that topic it will get the command.