This occurs when you need to set up cross domain requests and parameter Access-Control-Allow-Origin on the K2 server side for queries to REST endpoints in K2 4.7.
After changing the enableCrossDomainPolicy setting in the configuration file to "Enable", you keep getting the following error message in the web browser:
"No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access."
CORS settings for the SmartObject REST services are not supported.
The reason for this is that the REST service is hosted in the host server instead of IIS, which means there is no web.config file to configure CORS settings.
There is an existing feature request to implement this option. This functionality is only available in K2 Cloud. With K2 Five you can use OData services as an alternative.