Invalid CORS request

I am using fetch API to fetch data from the server (web application).
I have already set to allow CORS, in my config.xml file.
However, when I make a request to the server, an “invalid CORS request” error is shown.
If I allow every domain on the server-side (disable CORS), it works fine.
I think I should allow the domain of my Tizen web application on the server, but I am struggling to find the domain name of my Tizen app. (Currently, the origin of the domain is shown as null on the server-side)
Is there any way to check or set the domain name of the Tizen application?

Thank you