Webproxy, Webpanel, Webportal, Controlpanel

1. Open Google Chrome
2. Visit the URL where you login to the control panel or data center portal
3. Open Developer Tools From View > Developer > Developer Tools 
4. Open Network tab in the Developer Tools

5. Enter any random username and password in the respective form fields

6. Press enter key or click on the "Login" or similar button in the form

7. Wait till the process is complete (e.g. login failed message if you entered random username and password)

8. Select first one in the Name list and open Header tab

9. You can find the Request URL from the general section of ''headers tab". It will contain the protocol (https or http), host name or IP, port (if not the default for protocol), followed by request URI

9. Scroll the header tab and you can find  username and password field names

10. Check the values of parameters for the random string you entered for username and password fields in the login form to identify the parameter names.

11. The remaining parameters in the above tab should go into the extra variables. If there are some random value parameters, they may be ignored. When there are more than two extra parameters, they can be added in extra variables but joining them with & like: param1=value1&param2=value2