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Malicious Claude Code extension distributed via Cursor IDE marketplace

By PulseAugur Editorial · [10 sources] ·

A malicious version of the Claude Code extension was distributed through the Cursor IDE's marketplace on October 29, 2026. This tampered extension, versions 2.1.312 and 2.1.313, was available for approximately eleven hours and potentially affected up to 5,000 users. The malicious code aimed to install SSH backdoors, collect system details like hostnames and usernames, and establish persistence that could survive extension uninstallation. Anthropic has denied involvement, and neither Anthropic nor Cursor has fully explained how the attackers gained access to the marketplace account. AI

IMPACT This incident highlights supply chain risks for AI-powered developer tools, potentially impacting trust and security in AI-assisted coding environments.

RANK_REASON A security vulnerability was discovered in a third-party extension for an IDE, not a direct release from a frontier AI lab.

Read on Medium — AI coding tag →

AI-generated summary · Google Gemini · from 10 sources. How we write summaries →

Malicious Claude Code extension distributed via Cursor IDE marketplace

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Tool
A security vulnerability was discovered in a third-party extension for an IDE, not a direct release from a frontier AI lab.
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10 independent sources
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product, safety
Editorial topic classification. Feeds into how the story surfaces on /topic/<slug> hub pages and into the per-entity coverage mix.
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High
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3 days old
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+1 source(s) since last score
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Full methodology in our editorial standards.

COVERAGE [10]

  1. Medium — AI coding tag TIER_1 English(EN) · Vishal Shrestha ·

    Claude Code extension in Cursor was backdoored, so check your SSH keys

    <div class="medium-feed-item"><p class="medium-feed-image"><a href="https://vyshspace.medium.com/claude-code-extension-in-cursor-was-backdoored-so-check-your-ssh-keys-1c27836232d5?source=rss------ai_coding-5"><img src="https://cdn-images-1.medium.com/max/1600/0*j-idLpoQ6HvhZT06" …

  2. Medium — Claude tag TIER_1 English(EN) · Axythic ·

    Trojanized Claude Code Extension 2.1.313: How to Check and Clean Up

    <div class="medium-feed-item"><p class="medium-feed-image"><a href="https://medium.com/@axythic/trojanized-claude-code-extension-2-1-313-how-to-check-and-clean-up-7473ec72185b?source=rss------claude-5"><img src="https://cdn-images-1.medium.com/max/1200/0*KKV7eej08Y30P_pK.png" wid…

  3. Medium — Claude tag TIER_1 English(EN) · Circuit Bay ·

    The Claude Code extension backdoor in Cursor: what happened, and the one check to run

    <div class="medium-feed-item"><p class="medium-feed-image"><a href="https://medium.com/@circuitbay/the-claude-code-extension-backdoor-in-cursor-what-happened-and-the-one-check-to-run-87b10ac804a0?source=rss------claude-5"><img src="https://cdn-images-1.medium.com/max/920/0*5BSFZ2…

  4. Mastodon — fosstodon.org TIER_1 Italiano(IT) · [email protected] ·

    Cursor Distributes Infected Claude Code Extension: Thousands of Developers at Risk 📌 Article Link: https://www.redhotcyber.com/post/cursor-di

    Cursor distribuisce un’estensione infetta di Claude Code: migliaia di sviluppatori a rischio 📌 Link all'articolo : https://www. redhotcyber.com/post/cursor-di stribuisce-unestensione-infetta-di-claude-code-migliaia-di-sviluppatori-a-rischio/ Chiara Nardini # redhotcyber # cyberse…

    LINKS redhotcyber.com/…/cursor-distribuisce-une…
  5. Mastodon — mastodon.social TIER_1 Polski(PL) · [email protected] ·

    Malicious Claude Code update in Cursor Marketplace. Up to 5000 potentially affected users https:// sekurak.pl/zlosliwa-aktualizac ja-claude-code-

    Złośliwa aktualizacja Claude Code w Cursor Marketplace. Do 5000 potencjalnie poszkodowanych użytkowników https:// sekurak.pl/zlosliwa-aktualizac ja-claude-code-w-cursor-marketplace-do-5000-potencjalnie-poszkodowanych-uzytkownikow/ # Wbiegu # Ai # Bezpieczestwo # Claudecode # Curs…

    LINKS sekurak.pl/zlosliwa-aktualizacja-claude-c…
  6. Mastodon — mastodon.social TIER_1 Italiano(IT) · AI_BEAR_NEWS ·

    🔒 Malicious Extension for Claude Code Around 5,000 Cursor users may have installed a malicious extension that collected hostnames, usernames, system

    🔒 ESTENSIONE MALIZIOSA PER CLAUDE CODE Circa 5.000 utenti di Cursor potrebbero aver installato un'estensione malevola che raccoglieva hostname, username, sistema operativo e indirizzo IP. L'estensione è rimasta nel marketplace per sole 11 ore prima di essere rimossa. Fonte: The V…

  7. Mastodon — mastodon.social TIER_1 English(EN) · [email protected] ·

    Malicious # ClaudeCode extension on # Cursor planted # SSH backdoors https://www. bleepingcomputer.com/news/secu rity/malicious-claude-code-extension-on-cursor-

    Malicious # ClaudeCode extension on # Cursor planted # SSH backdoors https://www. bleepingcomputer.com/news/secu rity/malicious-claude-code-extension-on-cursor-planted-ssh-backdoors/ # Claude # AI # cybersecurity

    LINKS bleepingcomputer.com/…/malicious-claude-c…
  8. Mastodon — mastodon.social TIER_1 English(EN) · schuler ·

    A tampered Claude Code extension reached up to 5,000 Cursor users Oct. 29, attempting to install SSH backdoors and collect system details. Anthropic denies invo

    A tampered Claude Code extension reached up to 5,000 Cursor users Oct. 29, attempting to install SSH backdoors and collect system details. Anthropic denies involvement; neither company has explained how attackers accessed the marketplace account. https://www. implicator.ai/anthro…

    LINKS implicator.ai/anthropic-says-malicious-ac…
  9. Mastodon — mastodon.social TIER_1 Deutsch(DE) · [email protected] ·

    Claude Code — Million-times installed cursor extension compromised: Attackers have injected malicious code into the official cursor extension of Claude Code

    «Claude Code — Millionenfach installierte Cursor-Erweiterung kompromittiert: Angreifer haben Schadcode in die offizielle Cursor-Erweiterung von Claude Code eingeschleust. Tausende Entwicklersysteme sind betroffen.» Wenn ihr mich fragt, war das nur eine Frage der Zeit bis AI beim …

    LINKS golem.de/…/auswahl.html golem.de/…/auswahl.html
  10. r/cursor TIER_2 English(EN) · /u/Arelvox ·

    PSA: If you installed/updated the Claude Code extension in Cursor on Oct 29, check for this SSH backdoor (1-minute check)

    <!-- SC_OFF --><div class="md"><p>On Oct 29, from about 09:27 to 20:35 UTC, Cursor’s marketplace served tampered builds of the Claude Code extension (<strong>2.1.312 and 2.1.313</strong>). Anthropic says it didn’t build them, and Cursor says up to 5,000 users got them. VS Code (M…

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