simonwillison.net·May 26, 2026
Microsoft's Copilot Cowork has been found to allow users to send emails to their own inboxes without approval, posing a security risk as these messages could leak data through external images, potentially enabling attackers to exfiltrate files via pre-authenticated download links.
The key insight for you is the security risk highlighted by the recent issue with Microsoft Copilot Cowork, where agent-driven email actions could lead to data exfiltration via external images in emails. This underscores the importance of developing robust security measures in agentic AI systems to prevent unauthorized data leaks, particularly when dealing with prompt injection vulnerabilities.