By default, ArcGIS portals (including ArcGIS Online) allow cross-domain requests using Cross-Origin Resource Sharing (CORS). In the Esri portal used with Web Designer, if you have any domains configured in the Organization > Settings > Security > Allow Origins setting, then you must add the  server as an allowed origin.

•ArcGIS Online with SaaS Web Designer: If you use ArcGIS Online with SaaS Web Designer and your organization has configured the Allow Origins setting in ArcGIS Online, then you must add apps.vertigisstudio.com as an allowed origin.

•ArcGIS Online with On-Premises Web Designer: If you use ArcGIS Online with on-premises Web Designer and your organization has configured the Allow Origins setting in ArcGIS Online, then you must add your VertiGIS Studio Web Designer server as an allowed origin.

•On-Premises Portal for ArcGIS with On-Premises Web Designer: If you use an on-premises Portal for ArcGIS with on-premises Web Designer, and your organization has configured the Allow Origins setting in your portal, then you must add your VertiGIS Studio Web Designer server as an allowed origin.