Hidden prompts let Copilot alter and copy report data
📝 Security researcher Håkon Måløy disclosed that hidden, white-on-white instructions inside a Word document can make Microsoft 365 Copilot both rewrite report figures and copy those same instructions into the finished file. Microsoft acknowledged the behavior in March and deployed mitigations, including blocking the original prompt wording and upgrading the underlying model, but Måløy showed modified payloads still worked against later model versions. The technique requires a Copilot drafting or editing operation and that the malicious document enter the model's context, and it does not rely on conventional malware or zero-click exploitation.