Default admin password warning
GeoServer has a predefined admin user, which can be used to access GeoServer with full administration priviledges.
Required:
- The default password for the admin user must be changed to avoid unauthorized access to your GeoServer instance. 
Reference:
To change the password of the admin user
- Go to the GeoServer administration web page at [your GeoServer root url]/web (for instance: https://instance.geocat.live/geoserver/web )   
- Login using the login fields in the upper part of the page.   - Use admin as username and geoserver as password. 
- Now that you are logged in as an Administrator, the welcome page will list configuration warnings to be addressed. - Locate the warning: - > The administrator password for this server has not been changed from the default. It is highly recommended that you change it now. > Change it   - Default admin password warning 
- Click on the Change it to open the Edit user` page for the - adminuser:  
- Type in the new password to use for the admin user. 
- Press Save to save your changes.