Claude Code · Claude · Cursor · Apple · phorion.io
Phorion has discovered a compromise of the official Claude Code for VS Code extension on the Cursor Marketplace
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◎ Multiple-sources
While the implant includes setup and persistence logic for macOS, Linux, and Windows, phorion.io is going to focus primarily on macOS in this post, calling out the key differences and a few implementation bugs on the other platforms along the way.
Key facts
- It then sends the JSON report via plaintext HTTP POST requests to /beacon on both 134.209.82[.]225:8099 and 127.0.0.1:8099
- Update (31 October 2026): Cursor’s security notice now identifies versions 2.1.312 and 2.1.313 distributed through the Cursor Marketplace for macOS and Windows as affected
- Next, the script sets up an outbound SSH connection to 134.209.82[.]225 as the tunnel user on port 22
- Organisations should immediately review their environments for use of Claude Code for VSCode 2.1.312 or 2.1.313 and engage incident response where use of the extension is discovered
Summary
Phorion has detected a backdoor in the official Claude Code for VS Code extension bundle on the Cursor Marketplace that drops a persistent SSH backdoor across macOS, Linux, and Windows. Organisations should immediately review their environments for use of Claude Code for VSCode 2.1.312 or 2.1.313 and engage incident response where use of the extension is discovered. Update (31 October 2026): Cursor’s security notice now identifies versions 2.1.312 and 2.1.313 distributed through the Cursor Marketplace for macOS and Windows as affected. Phorion has discovered a compromise of the official Claude Code for VS Code extension on the Cursor Marketplace, where the backdoored extension bundle contains a persistent Secure Shell (SSH) backdoor.