Cybersecurity researchers disclosed that the official Anthropic Claude Code extension was compromised on the Open VSX registry, allowing the installation of a persistent SSH backdoor on infected hosts.
The vulnerability or weakness
The vulnerability involved a modified version of the extension that was not developed by Anthropic. It contained a 66-line malicious loader inserted before the legitimate code.
Earlier attacks and coverage
- Shadowy AI Relay Disables OpenAI Codex, Claude Code Sandboxes (2026-10-29)
- LiteLLM Compromised in Supply Chain Attack Delivering Credential Stealer and Backdoor (2026-10-21)
- Hackers Exploit Plex2Shell Flaws to Install Crypto Miners and Linux Proxy Backdoor (2026-10-19)
Business impact
This incident could lead to operational disruptions and data breaches, potentially harming Cursor's reputation. Affected users may face unauthorized access and data theft.
Industries affected
This affects developers and coders using VS Code, as the extension was distributed through the Cursor IDE extension marketplace.
Users affected
At most 5,000 users were impacted, and Anthropic has since released a new version to address the issue. Users should follow the remediation steps provided to secure their systems.
