Microsoft launches Application Guard for Office in public preview to protect enterprise users from threats using malicious attachments as an attack vector. Malicious Office documents are among the most common vectors exploited by threat actors to deploy malware such as ransomware, RATs, data-stealing trojans, and malware downloaders. The feature works with Word, Excel, and PowerPoint for Microsoft 365 and it will be off by default for customers with Microsoft 365 E5 or Microsoft 365 Security enterprise plans that can deploy it in their environments.
Source: https://www.bleepingcomputer.com/news/security/office-365-now-opens-attachments-in-a-sandbox-to-prevent-infections/