Affected Systems

Anthropic Claude Code extension version 2.1.313 distributed through Cursor Marketplace only (October 29, 2026, 2:27 AM - 1:35 PM PT). Up to 5,000 users affected. Extensions installed via Open VSX or Microsoft VS Code Marketplace are NOT affected. Impacts Windows, Linux, and macOS systems.

Exploitation Status

Active supply chain attack. Malicious version 2.1.313 was distributed under legitimate publisher identity (anthropic.claude-code) through compromised Cursor Marketplace. Removed as of October 30, 2026. Clean version 2.1.314 now available. Attack method for publisher compromise remains unknown.

Business Impact

Compromised systems have attacker SSH key added to ~/.ssh/authorized_keys (labeled "svc-telemetry"), reverse tunnel to 134.209.82.225, and platform-specific persistence (scheduled task/crontab/LaunchAgent). Backdoor exfiltrates host reconnaissance including public IP, hostname, username, OS details, Git email, and names of environment variables containing KEY, TOKEN, SECRET, PASS, AWS, or GCP. SSH service activation requires admin rights (often fails on macOS/Windows), but key installation and persistence succeed regardless. Successful SSH access enables arbitrary command execution and file transfer. No follow-on payloads observed yet.

Urgency

🔴 Immediate

Recommended Actions

  • Identify systems with Claude Code extension installed from Cursor Marketplace between October 29, 2026 2:27 AM - 1:35 PM PT and isolate them immediately
  • Remove unauthorized SSH key labeled 'svc-telemetry' from ~/.ssh/authorized_keys on all potentially affected hosts
  • Delete persistence mechanisms: Windows scheduled tasks, Linux crontabs, and macOS LaunchAgents created by the malicious extension
  • Block outbound connections to 134.209.82.225 (all ports) at network perimeter and inspect logs for prior connections to this IP on port 8099 or SSH tunnels
  • Rotate all credentials and API keys (especially AWS, GCP, CI/CD tokens) accessible from affected developer workstations and revoke active sessions
  • Update Claude Code extension to version 2.1.314 or later from Open VSX or Microsoft VS Code Marketplace only; avoid Cursor Marketplace until Cursor confirms full remediation