Part of AI Developer Tools Security Crisis · 2 stories · since Oct 28 · newest 9d ago
Fake Claude Code Extension on Cursor Marketplace Backdoored Up to 5,000 DevelopersAnthropic staff clarify the malicious build never touched official channels
6 Oct 30 12:10 PM · 13d ago · 3 articles · 18 posts · 47 comments · 6 sources · development 6 of 8
Anthropic employee Dworken states on Hacker News that version 2.1.313 was never published on OpenVSX, the VS Code marketplace, or any official host, and that Anthropic skipped that version number and shipped 2.1.314 to disambiguate.
“1.313 was never published on OpenVSX, the VS Code marketplace, or on any of our official hosts. The malicious actor here had published a fake version of this extension on Cursor's marketplace.”
Dworken (Anthropic)Anthropic Maker of Claude CodeCursor (Anysphere) Operator of the compromised extension marketplaceMichael Truell Cursor CEO (@mntruell)Phorion Security research firm that discovered the backdoorKevin Beaumont (GossiTheDog) Security researcher
The whole story articlespostscomments the bright band is this development · numbered dots are the others · click one to jump
Reported in the same hours no headline names this development itself — these 1 claim were published in its stretch
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first by The 420.in, 13d ago
What people said 24 voices · best of 59 · verbatim
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To be clear: Anthropic is on HN clarifying that this was exclusively distributed by the Cursor marketplace to Cursor. It didn’t come from Anthropic or any other marketplace. The perpetrators incremented the version number to get it to update, so Anthropic skipped that version number and released a new one, but the malware was never in their…
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This is the best coverage I've found so far of the Claude Code for VS Code backdoor: https://www. stepsecurity.io/blog/claude-co de-extension-trojanized The compromised version made it into all of the extension registries. Don't be misled by the fact that it was discovered first in the Cursor registry; this does _not_ just impact Cursor users, it…
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This is from the Cursor blog [1] linked in the description, but repeating it here because I found it useful:---Check whether you are impactedThe malicious extension appends the attacker's public key, labeled svc-telemetry, to your SSH authorized keys. To check for it:On macOS, run: grep -qs svc-telemetry ~/.ssh/authorized_keys && echo…
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I agree but this particular thing wasn't the fault of cursor, it would affect any IDE using open vsx which includes kiro, antigravity and windsurf on top of cursor
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There's statements from Anthropic employees over at [the orange site](https://news.ycombinator.com/item?id=50300683). Quoting a couple: > Dworken from Anthropic here, 2.1.313 was never published on OpenVSX, the VS Code marketplace, or on any of our official hosts. The malicious actor here had published a fake version of this extension on Cursor's…
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A malicious version of Anthropic's Claude Code VS Code extension was distributed through Cursor's extension marketplace for approximately 11 hours on October 29, exposing up to 5,000 developers to malware designed to install persistent SSH backdoors. https://www. bleepingcomputer.com/news/secu…
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> but it wasn’t a compromise of Anthropic’s systems or employee laptops.Seems a bit early to say.> A malicious actor used access to Cursor’s marketplace to publish a tampered copy of the Claude Code extension, which we didn’t build or publish.For a pretty limited definition of "we" true and obvious. For the interesting definition of "we", proven…
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Yes, people are throwing around a lot of speculation in this thread without evidence, and Anthropic is pretty flatly denying nearly all of that speculation on the record. See [the statements from Anthropic employees](https://news.ycombinator.com/item?id=50304129) on HN. I think it is important to be accurate about security incidents on a technical…
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RE: https:// cyberplace.social/@GossiTheDog /117528831681803563 As the story unfolds, it is getting more and more spectacular (and frightening): - Malware in widely used Claude extensions for both VS code and cursor - Gives ssh backdoor to where it is installed - Millions of installs on developer machines with potential access to thousands of…
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The situation is confusing, so can I please confirm the following:* "Cursor Editor" is a fork of VS Code* The "Claude Code for VS Code" extension, v2.1.313, was compromised specifically on the Cursor Editor extension marketplace / distribution system* The "Claude Code for VS Code" extension for regular VS Code on the official VS Code extension…
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I continue to not really be sure if I should be updating all my software to latest and greatest as often as I can for security, or never update anything ever again for security. Glad I'm not responsible for anything security related, I imagine folks in that domain must be living a nightmare right now.
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"Cursor VS Code extension used by tens of millions of developers for Claude access was delivering a remote access trojan via an SSH reverse backdoor. […] Anthropic has not informed customers, and the malicious version was silently deleted the backdoored version without telling anybody." cool. https:// doublepulsar.com/anthropic-hac…
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I'd suggest stop to use the word 'only' as it can be perceive wrongly here.you can simply say Cursor users were affected. or exclusively.just a tip from someone who worked tech support in cyber a long time. choice of words can really help change sentiments in these situations.'only server xyz was affected' vs. 'server xyz was affected' or…
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Ah yes, [the techno-amish (as invented by the author of the webcomic Freefall)](http://freefall.purrsia.com/ff3200/fc03150.htm). They use machinery and operating systems up to Windows XP (because living in space means the "simple life" has higher complexity requirements).
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There's a Claude Code extension for VS Code that quietly installed backdoor access. The release has been deleted and it sounds like the host that it was phoning hone to is offline, but the SSH backdoor is persistent: https:// cursor.com/blog/claude-code-ex tension-security-notice
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Ok, so... Summing this up- Cursor (obviously) is not using MSFT vscode extensions library - Cursor (apparently) is not using Open-VSX either! - Cursor uses it's own "Cursor's marketplace" which is not public, no one knows what it is exactly, and looks like it is proxying open-vsx marketplace (?) - THAT "Cursor's markeplace" is what was compromised…
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I was sceptical when Anthropic said their tools pose "existential risks to humanity", but it looks like for once they did not lie.
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Cursor posted on this on X. The Hacker News: Official Claude Code Extension on Cursor Marketplace Trojanized with Persistent SSH Backdoor https:// thehackernews.com/2026/10/offi cial-claude-code-vs-code-extension.html @ thehackernews # infosec # Claude # cyberattack # Anthropic
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I think right now AI is helping the attackers more than it's helping the defenders.That part is probably obvious.But in the long term, I suspect this will get worse.Attackers will still need to think critically to be a few steps ahead of the defenders.But the defenders will increasingly outsource their thinking to AI as they are incentived if not…
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Proper link, to the actual article rather than a social media repost:
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RE: https:// cyberplace.social/@GossiTheDog /117528831681803563 Of course this is a minimal impact problem as no dev in their right mind would run claude code on native hardware and keep it confined to a dedicated developer environment, right? ... Right?
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This is why when I use AI, I still download from the browser and drag and drop the outputted files like a caveman. Sure, it's slower, but it keeps my mental model more up to date and has less security risks. I can even...like read the thing before I run it rather than giving a LLM access to my shell directly. Also anecdotally, it seems more token…
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Nah, I am sure some of the Windows XP people could be grandmas.
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RE: https:// cyberplace.social/@GossiTheDog /117529314041166671 Oh dear, this does not bode well. Rhetorical question: what could possible go wrong when developer machines have been compromised with malware? 😩 CC: @ bert_hubert @ MarloesdeKoning
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