Anthropic VS Code extension backdoored for 11 hours

Key facts

• An official Anthropic VS Code extension for Claude was backdoored for nearly 11 hours.
• The compromised version, 2.1.313, affected up to 5,000 users via the Cursor marketplace.
• The backdoor attempted to install a persistent SSH backdoor and collect cloud credentials.
• Cursor and Anthropic have not publicly warned customers or explained the account compromise.
• The malicious code was designed to work on Windows, macOS, and Linux.

An official VS Code extension for Anthropic's Claude model was compromised for nearly 11 hours, potentially impacting up to 5,000 developers. The malicious version, 2.1.313, was distributed through Anthropic's official account on Cursor, an AI-assisted developer tool. The backdoor attempted to install a persistent SSH backdoor, collect host and user information, and gain access to local files and cloud credentials. The code was designed to work across Windows, macOS, and Linux. Cursor has since removed the malicious version, blocked its distribution, and reopened the VSCode Marketplace after implementing security measures. However, neither Anthropic nor Cursor has publicly warned customers or explained how the attackers gained control of the official distribution channel.