Microsoft 365 Copilot for Word can persist hidden prompt instructions

Intelligence Summary

A researcher demonstrated that hidden instructions embedded in a Word document can influence Microsoft 365 Copilot when drafting new content. The technique can cause Copilot to copy those hidden prompts into the resulting document during a drafting workflow. When the produced file is later reused in another Copilot session, the same behavior triggers again. This can lead to unintended instruction persistence and policy bypass if sensitive or malicious guidance is concealed in document metadata or content. Microsoft users should review documents for hidden content and treat shared Word files as potentially carrying instruction payloads. Administrators may want to monitor Copilot usage and enforce document handling policies for high-risk workflows.

Recommended Action

Review affected assets, schedule urgent remediation, and monitor related indicators.

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