Details
In order to directly pass the login information into the browser, you need to follow this syntax:
http://<ip>/pages/hmi/?user=<user>&pw=<password>
For example, if he camera's IP is 192.168.0.123 and you want to login the "operator" user that has "secret" as password, it would have to be this URL:
http://192.168.0.123/pages/hmi/?user=operator&pw=secret
Important note: This will only work as expected if the Admin user is locked with a password as well. Otherwise the HMI will always login as Admin.