Microsoft Copilot for Word Can Copy Hidden Prompts Into New Documents

Hidden instructions in a Word document can make Microsoft 365 Copilot rewrite figures in a report, then copy the same instructions into the finished file. Håkon Måløy disclosed the technique on July 28, 144 days after reporting it to Microsoft. In his proof of concept, the internally generated file triggered the same behavior when it was used in a second Copilot drafting session. Måløy's

The report describes a Microsoft Copilot for Word technique where hidden instructions in a document can be read by Copilot, then copied into a newly generated file, allowing the behavior to propagate through normal document workflows. Microsoft has described this broader pattern as indirect prompt injection, where hidden instructions inside content are treated as trusted input. RealGround relevance: this is a high-priority prompt-injection and data-governance risk for Copilot deployments, especially where agents can process internal documents and reuse generated outputs across workflows.