Microsoft has seen 400,000 attempted macro-rooted computer compromises in the last few weeks. Microsoft has decided to bring Application Guard to Office 365. Application Guard is the same security feature thats in the Edge browser in Windows 10. Microsoft is offering a limited preview of Application Guard for the ProPlus version of Office 365. If someone wants to designate a document as trusted that had been considered untrusted, it will be flicked to the Defender ATP threat cloud to ensure it is not malicious.”]
Source: https://www.cuinfosecurity.com/malicious-macros-problem-may-be-solved-soon-a-13361