Self-Propagating AI Worm Discovered in Microsoft Word Copilot

A critical vulnerability in Microsoft Copilot for Word allows hidden malicious prompts in documents to alter generated content and spread to new files. Disclosed by researcher Håkon Måløy, this issue, termed 'Context Collapse, Part 3 – AI Worming through Word,' has persisted despite Microsoft's mitigation attempts since March 2026. The vulnerability enables attackers to exploit untrusted documents without requiring access to a victim's Microsoft 365 tenant. Måløy's research indicates that the worm can propagate through normal workflows, making it difficult to trace its origin. Microsoft has acknowledged the issue but has not yet provided a robust solution. The attack vector relies solely on the inclusion of a compromised document in Copilot's context. The situation remains urgent as the worm continues to pose a significant risk to businesses using Microsoft Word.

Key Points: • A self-propagating worm can alter documents and spread through Microsoft Word Copilot. • The vulnerability allows hidden malicious instructions without needing access to the victim's tenant. • Microsoft's mitigation efforts have failed to close the broader vulnerability class.