Part of AI Developer Tools Security Crisis · 2 stories · since Oct 28 · newest 8d ago
Fake Claude Code Extension on Cursor Marketplace Backdoored Up to 5,000 DevelopersArs Technica reports backdoor was live for nearly 12 hours
7 Oct 30 5:09 PM · 12d ago · 3 articles · 11 posts · 12 comments · 6 sources · development 7 of 8
Dan Goodin reports the compromised extension was available for close to 12 hours and that it remains unknown how attackers obtained access to Anthropic's verified Cursor publishing account.
“It's still unknown how attackers got access to Anthropic's verified Cursor account.”
Dan GoodinAnthropic 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 2 claims were published in its stretch
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first by Microsoft, 12d ago
1 more headline
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first by Dark Reading, 12d ago
What people said 17 voices · best of 18 · verbatim
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As far as I can tell, you can't upload directly to Cursor's VSCode extension marketplace and there is no such thing as a "Cursor Marketplace account" (in the relevant sense; there is a separate marketplace not for VSCode extensions that you can upload to, but that's not where the compromised extension lived). You can only upload to OpenVSX, which…
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Dan wrote about the Cursor back door. As Brian chess said this morning, "...this is just vanilla software security. In that sense it's a distraction, but it's hard to get 2026 right if you're still struggling with the lessons from 2006." Right you are, Dr chess. # swsec # appsec # MLsec https:// arstechnica.com/security/2026/…
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You can say that this isn't compromise of Anthropic, but it sort of is in the setup. Cursor Claude extension is marked as something made by Anthropic, so default assumption is that only people who can release that new extension would be a team at Anthropic.Since that is clearly not the case, that is just as much Anthropic's problem as it is…
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Oh I know a ton of people like this and they're all women.
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"Phorion has detected a backdoor in the official Claude Code for VS Code extension bundle on the Cursor Marketplace that drops a persistent SSH backdoor across macOS, Linux, and Windows. This write-up focuses primarily on macOS, where the extension attempts to configure an SSH backdoor and establish persistence. Organisations should immediately…
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Cursor's "marketplace proxy" is, by definition, an MitM of Open VSX. Why on earth is that trustworthy to its users? Is it some mashup of Open VSX Connect and an API endpoint that merges their private marketplace with the public one? And what's so special about Cursor's CC extension implementation that they couldn't just serve the "real" one?Or are…
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Ah yeah, all the companies IT tells you to trust. Always the same story. Just like CrowdStrike, etc. Maybe just don't trust huge complex supply chains and systems with everything? I think one needs to learn from real world security and make sure that even when there is complexity the failsafe is simple and nobody messes with it. Because even in…
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Trojanized Claude Code Extension Plants SSH Backdoor in Cursor Marketplace A malicious version of the Claude Code extension (v2.1.313) was distributed through the Cursor Marketplace, installing a persistent SSH backdoor and exfiltrating developer environment metadata. **If you installed the Claude Code extension from the Cursor Marketplace, update…
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This kind of thing is only going to get worse. People assume other devs are "like them" but state actors (think US, NK, RS, CN) are likely using AI at this point to run agents non-stop to break security by making dev tools or contributing to open source. Keep in mind that open source is the backbone of nearly all software being used - we're in for…
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So, who is at fault here then? Was that a breach in Cursor Marketplace itself? Or did they get access to the Cursor Marketplace account of the person responsible for uploading the extension?
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As a friend put it, rough day for Cursor... https:// cursor.com/blog/claude-code-ex tension-security-notice
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I only use the VS Code version, but the lack of official statement from Anthropic around this has affected my trust in their ability to coordinate against future security issues (no, having your individual employees respond doesn't count as a statement).I mean, why was the Cursor package marked as verified Anthropic if it wasn't actually them? Why…
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[Sandbox](https://github.com/ashishb/amazing-sandbox#run-vscode-and-its-potentially-malicious-extensions-inside-the-sandbox-on-mac-os) your VS code executions.
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RE: https:// cyberplace.social/@GossiTheDog /117519256602179261 I think that clears it up.
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If I were Anthropic, I'd consider removing the official extension until Cursor get their act together and fix the problem that resulted in brand-damaging headlines for Anthropic.
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The unfortunate part about this is that the Anthropic account on OpenVSX published the newer version, which makes it look like they fixed the issue on OpenVSX.
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A glaring failure by Cursor's security team. During threat modelling, could anything be more obvious to identify?
All 8 developments of Fake Claude Code Extension on Cursor Marketplace Backdoored… →
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