Malicious Claude Code extension on Cursor planted SSH backdoors
Version 2.1.313 was listed for about 11 hours on October 29 and may have reached 5,000 developers.
A modified Claude Code extension in Cursor’s marketplace ran a JavaScript loader as soon as it loaded, adding an attacker SSH key, persistence, and a reverse tunnel. Coding errors often stopped the malware from turning SSH on, so many Windows and macOS hosts may not have been remotely reachable. Recon data was still sent to 134.209.82.225. Cursor removed the listing, audited the marketplace, and said no other versions or the official distribution were affected.
Unconfirmed: How the package was published under Anthropic’s name, and whether Cursor or Anthropic systems were compromised, is unanswered.
- The package was available from 2:27 a.m. to 1:35 p.m. Pacific Time on October 29.
- Persistence used a macOS LaunchAgent or a Windows scheduled task or Startup script.
- Look for an SSH key named svc-telemetry on machines that installed the package.
- Later checks found Cursor was the only marketplace that distributed it.
Impact: Persistent SSH access and host reconnaissance, if the tunnel succeeded
| Product | Affected |
|---|---|
| Anthropic Claude Code VS Code extension | 2.1.313 on Cursor’s marketplace |
- 1.Check for an svc-telemetry SSH key if the extension was installed on October 29.
- 2.Isolate confirmed hosts, rotate accessible secrets, and rebuild from safe backups.
- ATT&CK
- T1195.002 Compromise Software Supply ChainT1098.004 SSH Authorized KeysT1053.005 Scheduled TaskT1543.001 Launch AgentT1021.004 SSH
- Products
- Claude Code
- Organizations
- PhorionOpenSourceMalware
Indicators of compromise
auto-extracted · verify before use · export allAll| Type | Indicator | Context |
|---|---|---|
| ipv4 | 134.209.82.225 | backdoor status to the attacker’s server at the IP address 134.209.82[.]225 Attack chain Source: OpenSourceMalware However, according |
From the original article
3 min read at bleepingcomputer.com
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. [...]
By Bill Toulas · bleepingcomputer.com
A short excerpt; the article and its images belong to the publisher. Summary, key facts and assessment above are AI-written from the article and can be wrong.