Microsoft Teams: File Image preview in chats and channels

🚨 The Signal: Microsoft Teams now displays file image previews for Word, Excel, PowerPoint, and PDF documents in chats. This change allows users to view document thumbnails without opening the file, potentially exposing sensitive content to unintended recipients or in unapproved contexts.

The Impact

All Teams users are affected, increasing the risk of accidental sensitive data exposure through visual previews.

• End users: Risk of inadvertently exposing sensitive document content via thumbnails.
• Security Team: Increased challenge in preventing and detecting accidental data leakage.
• Compliance Officers: New vector for non-compliance with data handling and privacy regulations.

The Action

1. Review existing Microsoft Purview Data Loss Prevention (DLP) policies to ensure they account for visual content exposure in Teams.
2. Educate users on the implications of file previews and the importance of careful sharing, especially for sensitive documents.
3. Consider implementing or refining sensitivity labels for documents that should never have visual previews in unapproved contexts.

Domain: Teams · Impact: medium · Workload: Teams