Misbehavior1 sourceFirst seen 05/04/2026

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Copirate 365: A Poisoned Word Doc Turned Microsoft's Copilot Against Its Own User

Ourtake

Memory on by default, audit logs off by default. Trust No AI, and assume the chatbot will read whatever you hand it.

What happened

A security researcher showed that hidden prompt injections in shared documents could make Microsoft 365 Copilot leak data, such as emails, through HTML preview font requests, and write persistent false memories. Microsoft assigned CVE-2026-24299 and marked the issues fixed on March 5, 2026, after disclosures starting in October 2025.

Source

embracethered.com · 05/04/2026Copirate 365 at DEF CON: Plundering in the Depths of Microsoft Copilot (CVE-2026-24299) (opens in a new tab)