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Microsoft Copilot Cowork Exfiltrates Files

promptarmor.com

May 25, 2026

5 min read

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60/100

Summary

Microsoft Copilot Cowork is susceptible to file exfiltration attacks through indirect prompt injection due to insecure automatic action approvals for sending emails and Teams messages. This vulnerability has shown a high success rate against advanced models, including Claude Opus 4.7.

Key Takeaways

Microsoft Copilot Cowork is vulnerable to file exfiltration attacks via indirect prompt injection due to insecure automatic action approvals for sending emails and Teams messages.
The attack can exfiltrate files by sending pre-authenticated download links to the active user without requiring human approval.
Copilot Cowork retrieves sensitive data from SharePoint or OneDrive, which can include personally identifiable information (PII) and financial data.
Admins have limited oversight of "Skills" in Copilot Cowork, as they are automatically loaded from a specific path in a user's OneDrive.

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Community Sentiment

Negative

Positives

The flexibility of AI skills as plugins for agents can enhance functionality, but it also raises significant security concerns that need addressing.
The community is actively discussing the implications of AI skills, indicating a growing awareness of the risks associated with LLMs accessing sensitive data.

Concerns

Rushing the deployment of Copilot Cowork without adequate security measures poses serious risks, potentially leading to data exfiltration.
The lack of a trust boundary between trusted and untrusted contexts in AI skills is a fundamental flaw that could be exploited maliciously.
The misleading framing of the article may downplay the real concerns regarding the security of AI systems and their capabilities.