Prompt turns Microsoft Copilot into an AI worm
The technique allows an attacker to hide a JSON‑formatted prompt as white text on a white background inside a Word document. When someone asks Copilot for Word to draft or edit content based on that document, Copilot strips away the formatting, reads the hidden text, and treats the embedded instructions as part of the user’s request. Copilot then modifies the active document and appends the full malicious prompt as hidden white text.
- ▪The technique allows an attacker to hide a JSON‑formatted prompt as white text on a white background inside a Word document.
- ▪When someone asks Copilot for Word to draft or edit content based on that document, Copilot strips away the formatting, reads the hidden text, and treats the embedded instructions as part of the user’s request.
- ▪Copilot then modifies the active document and appends the full malicious prompt as hidden white text.
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Story provenance
Source · retrieval · rights · ranking — open for full record
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Story provenance
Attribution is not the same as permission. This drawer separates discovery metadata, excerpts, WeSearch-generated summaries, reuse status, and whether the publisher receives the visit. Nothing here claims a legal grant the publisher has not made.
Record
| Original publisher | Malwarebytes |
| Canonical URL | https://www.malwarebytes.com/blog/ai/2026/07/hidden-microsoft-copilot-ai-worm |
| Publication time | Thu, 30 Jul 2026 15:35:30 +0000 |
| Retrieval time | 2026-07-30T15:37:05.185Z |
| Last seen | 2026-07-30T15:37:05.185Z |
| Headline source | Publisher (no WeSearch rewrite) |
| Excerpt source | publisher body |
| Excerpt method | First ~120 words (~800 chars) of extracted publisher body, fair-use limited. |
| Summary | WeSearch · cerebras-chat (WeSearch summarizer) |
| Summary source text | contentText |
| Citation coverage | Summary is a WeSearch-generated derivative; primary citation is the original publisher URL. |
| Cluster | L2ebWqSxhaFd · 1 stories |
| Cluster logic | Grouped by semantic title/content similarity across sources within a rolling window. Same-publisher template collisions are excluded from coverage comparison. |
| Ranking reason | Story pages are not engagement-ranked. Hub feeds use recency, with optional source-diversified chronological ordering (cap consecutive stories per source). No personalized ranking. |
| Publisher visit | Yes — open original |
| Substitutes article? | No — link-out required for full text |
Rights status (four layers)
WeSearch handling by dimension
| Indexing | May the item be indexed (stored, ranked, made findable)? | Allowed |
| Snippet | May a short excerpt of the publisher's text be shown? | Allowed |
| AI summary | May WeSearch generate its own short summary of the article? | Limited |
| Retrieval / RAG | May the content be exposed for third-party retrieval-augmented generation? | Not asserted |
| Model training | May the content be used to train AI models? | Not asserted |
| Commercial reuse | May the content be reused commercially? | Not permitted |
Basis: Derived from the published RSS/Atom feed. Contact: [email protected]. Reviewed: 2026-07-24.
Opening excerpt (first ~120 words) tap to expand
A security researcher has demonstrated how Microsoft Copilot for Word can be tricked into spreading a self‑propagating prompt‑injection “AI worm.” The attack silently alters documents and embeds its own hidden instructions into newly created files, allowing it to spread through normal document-sharing workflows without macros or traditional malware. The technique allows an attacker to hide a JSON‑formatted prompt as white text on a white background inside a Word document. When someone asks Copilot for Word to draft or edit content based on that document, Copilot strips away the formatting, reads the hidden text, and treats the embedded instructions as part of the user’s request. Copilot then modifies the active document and appends the full malicious prompt as hidden white text.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at Malwarebytes.
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