--- title: Microsoft Copilot’s ‘Word worm’ still works 144 days... description: A Norwegian researcher disclosed a self-propagating 'AI worm' that exploits Microsoft Copilot for Word via prompt injection hidden in white-on-white text. The... canonical: https://daily.dev/posts/microsoft-copilot-s-word-worm-still-works-144-days-after-disclosure-d8jqffsat twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Microsoft Copilot’s ‘Word worm’ still works 144 days after disclosure | daily.dev og:description: A Norwegian researcher disclosed a self-propagating 'AI worm' that exploits Microsoft Copilot for Word via prompt injection hidden in white-on-white text. The... og:url: https://daily.dev/posts/microsoft-copilot-s-word-worm-still-works-144-days-after-disclosure-d8jqffsat og:image: https://api.daily.dev/og/posts/D8jQFFSAt.png og:image:alt: Microsoft Copilot’s ‘Word worm’ still works 144 days after disclosure og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Microsoft Copilot’s ‘Word worm’ still works 144 days after disclosure **[The Next Web](https://daily.dev/sources/tnw)** · 4 min read · 0 upvotes · 0 comments ## Summary A Norwegian researcher disclosed a self-propagating 'AI worm' that exploits Microsoft Copilot for Word via prompt injection hidden in white-on-white text. The malicious instructions alter document content (e.g., halving financial figures) and copy themselves into output files, spreading hop-by-hop through normal Copilot workflows. Microsoft confirmed the issue in March, shipped two fixes including a model upgrade to GPT-5.5, but the researcher rewrote the payload and it worked again on GPT-5.6 the next day. The researcher argues the vulnerability is architectural: a model must read attacker-controlled content to judge whether it is an attack, making model-level defenses fundamentally unreliable. The disclosure comes as Microsoft aggressively expands Copilot into a 'super app' with 30 million paid seats and 60% revenue growth. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Microsoft Copilot Cowork Exfiltrates Files](https://daily.dev/posts/microsoft-copilot-cowork-exfiltrates-files-m799kd5a0) · Hacker News · 0 upvotes · 0 comments --- Tags: [#microsoft](https://daily.dev/tags/microsoft), [#llm](https://daily.dev/tags/llm), [#ai-security](https://daily.dev/tags/ai-security), [#prompt-injection](https://daily.dev/tags/prompt-injection), [#microsoft-copilot](https://daily.dev/tags/microsoft-copilot) [View this post on daily.dev](https://daily.dev/posts/microsoft-copilot-s-word-worm-still-works-144-days-after-disclosure-d8jqffsat) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Microsoft Copilot’s ‘Word worm’ still works 144 days after disclosure","url":"https://daily.dev/posts/microsoft-copilot-s-word-worm-still-works-144-days-after-disclosure-d8jqffsat","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/microsoft-copilot-s-word-worm-still-works-144-days-after-disclosure-d8jqffsat"},"datePublished":"2026-07-30T15:07:11.099Z","dateModified":"2026-07-31T03:40:02.425Z","description":"A Norwegian researcher disclosed a self-propagating 'AI worm' that exploits Microsoft Copilot for Word via prompt injection hidden in white-on-white text. 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