Why is grafana datasource proxy available outside grafana?

I have implemented a custom datasource that uses grafana proxy. All the requests to external API goes through this proxy and it’s going well. So the requests goes through address: http://localhost:3000/api/datasources/proxy/uid/XYZ/my-api/tables where localhost:3000 is where I have my grafana instance. But I found out that the proxy is visible outside grafana and I can make the same requests from outside (ex. Postman). I would expect that call from outside will return me an error but it’s not.
Shouldn’t proxy address be accessible only from inside grafana? Am I missing some configuration there?

Thanks for help