Official Claude Code extension compromise
A backdoored version of the Claude Code extension for VS Code was discovered on the Cursor Marketplace, potentially exposing developer environments to SSH-based attacks. Security researchers have advised organizations to audit their systems and remove the compromised version 2.1.313.
Why it matters
This incident highlights the supply chain risks inherent in third-party IDE extensions, which can grant attackers deep access to sensitive source code and developer credentials.
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. This write-up focuses primarily on macOS, where the extension attempts to configure an SSH backdoor and establish persistence.
Organisations should immediately review their environments for use of Claude Code for VSCode 2.1.313 and engage incident response where use of the extension is discovered.
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. Cursor has removed the associated release from its marketplace, additionally pulling NPM and VSCode versions for 2.1.313 from their relevant registries.
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