
Explanation:

To have a Microsoft Sentinel workbook pull live data from an external web service, you use the workbook's built-in JSON data source. Workbooks can query REST endpoints that return JSON and render results dynamically in visuals. Because the Azure portal (where the workbook runs) is a different origin than your on- prem/public Webapp1 , browsers will block these cross-origin requests unless the endpoint explicitly allows them. Therefore, the external service must enable CORS to permit the portal's origin to fetch the JSON. This aligns with Microsoft guidance that Workbooks can query HTTP/HTTPS JSON endpoints and that external endpoints must allow cross-origin requests for client-side calls from the Azure portal. Enforcing CORS on Webapp1 satisfies the security model while enabling the workbook to retrieve data at view time-meeting the requirement to "dynamically retrieve data from Webapp1." Options like "custom endpoint" or "custom resource provider" aren't needed here, and enabling SOP or only enforcing TLS 1.2 wouldn't address the browser's cross-origin policy blocking the call.