Azure AD B2B Close Security Issue: Only allow directly shared Apps

[rmalone]

The new B2B feature is great and will allow many new use-cases, but it opens up a ALL Apps shared with the Entire Organization to any guest user. This should be fixed! Guest users should only view what was directly shared with them. It's understood the Power BI Admin can disable sharing with the Entire Org, but this is a handy feature to share company wide data.