Sounds like you’re trying the REST call via the browser? You need to pass the authentication details along with the REST call. You can do that by either first logging into the WebPortal in the same browser, or by explicitly adding the basic auth (or a JWT) along with the request.
Could you explain in a little more detail exactly how you are calling the KNIME Server?
It’s definitely possible to modify the Access-Control-Allow-Origin header. The link that Jon provided above will allow you to configure this within the TomEE server that the KNIME Server is running on.
If you’re not comfortable with SSH and modifying config files then I would first suggest trying out another non-browser based REST client.
I would recommend Insomnia or Advanced REST Client
I would be surprised if you are still seeing this messages from one of these clients and if that’s the case then there is a different problem going on here. Possibly something unusual with your network configuration or proxies.
Editting the configuration to remove the CORS problem would also work if you are happy with that, we can also provide more assistance there if the link above isn’t informative enough.
Apologies that this has taken a while to resolve for you, it’s not something we’ve been able to reproduce ourselves, my own version of postman does not show this error (and as far as I’m aware, can’t produce this error).