Malicious Claude Code extensions found in Cursor marketplace, planted SSH backdoors
DavidLinthicum · x · 2026-11-03
Cursor disclosed that two malicious versions of the Anthropic Claude Code extension (2.1.312 and 2.1.313) appeared in its VS Code Extension Marketplace for macOS and Windows. Not built by Anthropic, but branded with its name and targeting Claude Code users.
Once installed, the malicious extension would collect host/user data, add an attacker-controlled SSH key, enable local SSH, open a reverse SSH tunnel, and establish persistence.
The author argues that as AI coding tools embed deeper into IDEs, terminals, credentials, and build systems, the supply-chain attack surface is now concrete — and Anthropic's security posture is once again under scrutiny.
Related event: Cursor Marketplace Hacked with AI Backdoor in Claude Code Extensions(2 posts)→
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