Microsoft Copilot (Microsoft 365): Shared mailbox access for emails in Copilot Chat

🚨 The Signal: Copilot Chat can now access shared mailboxes, allowing users to ground conversations in shared email data. This expands the data accessible to Copilot, increasing potential for sensitive information exposure if not governed.

The Impact

All users with shared mailbox access are affected, increasing the risk of sensitive information exposure via Copilot.

• End users: Risk of inadvertently exposing sensitive shared mailbox content through Copilot conversations.
• Security teams: Increased surface area for data leakage and compliance violations within Copilot.
• Data owners: Need to re-evaluate data sensitivity and access controls for shared mailboxes.
• Compliance officers: New considerations for data handling and retention policies within Copilot's scope.

The Action

1. Review existing shared mailbox access permissions to ensure least privilege is enforced.
2. Implement or refine Microsoft Purview Data Loss Prevention (DLP) policies for Copilot to prevent sensitive data exfiltration from shared mailboxes.
3. Educate users on responsible AI usage, data sensitivity, and the implications of grounding Copilot in shared mailbox content.
4. Monitor Copilot usage logs for unusual access patterns or data interactions involving shared mailboxes via Microsoft Purview Audit.
5. Assess and update information protection labels (Microsoft Purview Information Protection) for shared mailbox content.

Domain: Agentic-AI · Impact: high · Workload: Exchange Online