Issue:
While configuring replica mentioning MASTER_USER and MASTER_PASSWORD is not safe as we get a warning for the same.

example:

As result not mentioning MASTER_USER and MASTER_PASSWORD in CHANGE MASTER TO command and mentioning MASTER_USER and MASTER_PASSWORD while starting replica as follows,

As we can see in the metadata table mysql.slave_master_info, User_name and User_password is blank.

All good at this point.

Now when the replica mysql server restarted, replication starts automatically and failed with error,

Last_IO_Error: error connecting to master 'test@127.0.0.1:23609' - retry-time: 60 retries: 1

example:

Expectation:
As we can see in the example it's trying to start replication with a test username, but we did not use test user or have in mysql server user list. So username should be blank in "show slave status" and in mysql.slave_master_info and should NOT use any default user which is confusing for the user.

 Test: