Affected Systems

Cursor IDE extension marketplace, October 29, 2026, 2:27 AM - 1:35 PM PT. Malicious Claude Code extension version 2.1.313. Up to 5,000 developers potentially exposed. Official VS Code, npm, and Open VSX marketplaces were NOT affected.

Exploitation Status

Active supply chain attack. Malicious extension distributed for 11 hours. Attacker infrastructure (134.209.82.225) was taken offline. SSH backdoor functionality partially failed due to coding errors on Windows and macOS systems without SSH already enabled, but reconnaissance data was still exfiltrated.

Business Impact

Developers who installed the malicious extension during the exposure window are at risk of persistent SSH backdoor installation and credential exposure. The malware collected system information, Git email addresses, public IP addresses, and environment variable names associated with credentials. While SSH backdoor setup failed on many systems due to privilege and platform errors, attackers still received reconnaissance data. Any code, credentials, or secrets accessible from compromised developer workstations should be considered exposed. Supply chain mechanism remains unclear—unknown whether Cursor or Anthropic infrastructure was compromised.

Urgency

🔴 Immediate

Recommended Actions

  • Identify all developers using Cursor IDE who may have installed extensions on October 29, 2026 between 2:27 AM and 1:35 PM PT
  • On potentially affected systems, search for SSH key named 'svc-telemetry' in ~/.ssh/authorized_keys (Linux/macOS) or C:\ProgramData\ssh\administrators_authorized_keys (Windows)
  • Check for persistence mechanisms: macOS LaunchAgent files in ~/Library/LaunchAgents/ or /Library/LaunchAgents/, Windows scheduled tasks or Startup folder scripts related to SSH tunneling
  • Rotate all credentials, API keys, and tokens accessible from affected developer workstations, including Git credentials, cloud provider keys, and internal service accounts
  • Review outbound connections to IP 134.209.82.225 in firewall and proxy logs from October 29-30, 2026 to identify compromised systems
  • Isolate confirmed impacted machines, invalidate active sessions, and rebuild from known-good backups or clean OS images