Cross-domain iframe requests are blocked in SharePoint Online
Cross-domain iframe requests to SharePoint Online organizations are blocked.
This issue occurs when one of the following conditions is true:
You're displaying SharePoint Online pages on an external site through an iframe.
You're displaying SharePoint Online pages on a SharePoint Online site that uses a different domain through an iframe.
For more information about iframing SharePoint-hosted pages in applications, go to IFraming SharePoint-hosted pages in apps.
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