Claude Code extension poisoned with persistent SSH backdoor

# Claude Code extension poisoned with persistent SSH backdoor

https://gcdradar.vercel.app/incidents/claude-code-extension-poisoned-with-persistent-ssh-backdoor · AIR-2026-1664 · live

- Lane: Supply chain
- Severity: 3 (Confirmed exploitation): Confirmed malicious package distribution in the wild.
- Fix status: No patch yet
- First reported: 2026-10-30
- AI role: Attack on AI
- Products: Claude Code extension

## Summary

A tampered build of Anthropic’s Claude Code extension planted an SSH backdoor on developers’ machines via the Open VSX marketplace. Researchers discovered the malicious version 2.1.313 distributing unauthorized access.

## What to do

Remove the malicious Claude Code extension version and check systems for unauthorized SSH keys.

## Affected and fixed versions

- Affected: Claude Code extension 2.1.313

## Latest updates

- 2026-10-30: Report confirms exposure duration of 11 hours and up to 5,000 developers affected on the marketplace (https://bleepingcomputer.com/news/security/malicious-claude-code-extension-on-cursor-planted-ssh-backdoors)
- 2026-10-30: Official Claude Code Extension on Cursor Marketplace Trojanized with Persistent SSH Backdoor (https://thehackernews.com/2026/10/official-claude-code-vs-code-extension.html)
- 2026-10-30: Claude Code extension poisoned with persistent SSH backdoor (https://helpnetsecurity.com/2026/10/30/claude-code-extension-ssh-backdoor)

## Sources

- 2026-10-30 Help Net Security: Claude Code extension poisoned with persistent SSH backdoor https://helpnetsecurity.com/2026/10/30/claude-code-extension-ssh-backdoor
- 2026-10-30 The Hacker News: Official Claude Code Extension on Cursor Marketplace Trojanized with Persistent SSH Backdoor https://thehackernews.com/2026/10/official-claude-code-vs-code-extension.html
- 2026-10-30 BleepingComputer: Malicious Claude Code extension on Cursor planted SSH backdoors https://bleepingcomputer.com/news/security/malicious-claude-code-extension-on-cursor-planted-ssh-backdoors
- 2026-10-31 Microsoft Security: Inside a malicious Claude Code-branded extension and its persistent SSH backdoor https://microsoft.com/en-us/security/blog/2026/10/30/inside-malicious-claude-code-branded-cursor-extension-persistent-ssh-backdoor
- 2026-11-02 SecurityWeek: Malicious Claude Code Extension Served in Cursor Supply Chain Attack https://securityweek.com/malicious-claude-code-extension-served-in-cursor-supply-chain-attack

Verify against the vendor's advisory before changing production. Data CC BY-SA 4.0, https://gcdradar.vercel.app.