# Cursor finds SSH backdoor in fake Claude Code extension

Digest AI · Society & Work · published 2026-10-30T08:05:08Z

Canonical: https://digestai.news/story/cursor-finds-ssh-backdoor-in-fake-claude-code-extension

## Summary

Cursor disclosed a security breach on October 29, 2026, after detecting a malicious version of the *Anthropic.claude-code* VS Code extension in its marketplace. The package, version **2.1.313**, was not developed by *Anthropic* and attempted to install a persistent SSH backdoor on up to **5,000** users. It ran between **2:27 a.m. PT** and **1:35 p.m. PT** on October 29, 2026, before Cursor removed it and shut down the marketplace for a precautionary rebuild.

The extension collected system details—hostname, OS, Git email, and IP address—and tried to add an attacker-controlled SSH key to users’ authorized keys files. While the reverse SSH tunnel failed on most systems due to missing admin privileges, it still installed persistence mechanisms (LaunchAgent on macOS, scheduled tasks on Windows) and sent data to an attacker-controlled endpoint at **134.209.82.225:8099**. Cursor confirmed the attacker’s server was taken offline, but users are advised to check for lingering backdoors using provided scripts and rotate credentials if affected. The company emphasizes the incident only involved the tampered extension and not the official *Anthropic* distribution.

## Key points

- Attempted SSH backdoor via reverse tunnel, persistence scripts, and data exfiltration to attacker’s **134.209.82.225:8099**
- Cursor shut down marketplace, removed malicious package, and provided remediation scripts for affected users

## Why it matters

A successful attack on a widely used VS Code extension could expose developer systems to credential theft and remote access. The incident highlights risks of tampered third-party tools and underscores the need for stricter marketplace security.

## Sources

1. [Cursor Discloses SSH Backdoor Attempt in Malicious Claude Code Extension](https://unite.ai/cursor-discloses-ssh-backdoor-attempt-in-malicious-claude-code-extension) (Unite.AI, 2026-10-30)

Part of the developing story: [AI Coding Assistants Face Rising Security Threats](https://digestai.news/thread/researchers-show-ai-coding-agents-can-be-hijacked-via-malicious-agents-md-files) (4 stories)

## Cite

Digest AI, "Cursor finds SSH backdoor in fake Claude Code extension", 30 October 2026, https://digestai.news/story/cursor-finds-ssh-backdoor-in-fake-claude-code-extension

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