GoKawiilBackdoored Claude Code VS Code extension found on Cursor Marketplace
Security firm Phorion identified that version 2.1.313 of the official Claude Code extension for VS Code, distributed via the Cursor Marketplace, contained a hidden SSH backdoor targeting macOS, Linux, and Windows systems. Cursor has since removed the affected release from its marketplace and pulled the corresponding NPM and VS Code packages from their registries.
GoKawiil's interpretation of the reporting above, not reported fact.
Because extensions run with the same permissions as the IDE and its user, a compromised package can grant attackers immediate access to source code, credentials, and developer machines without further exploitation. Phorion's analysis suggests the attackers' macOS persistence logic contained a coding flaw that unintentionally prevented SSH from being enabled on systems where it wasn't already active, which may have limited real-world impact for some users. Organisations that installed the affected version are advised to treat any instance as potentially compromised and begin incident response.
- Claude Code for VS Code version 2.1.313 on the Cursor Marketplace contained a backdoor that attempted to install persistent SSH access.
- Cursor has removed the compromised release and corresponding NPM and VS Code packages from its registries.
- A bug in the macOS persistence script may have prevented SSH from actually being enabled on some affected systems, though keys and persistence mechanisms were still installed.
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Published there as: “Official Claude Code extension compromise”
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