# Compromised Claude Code Extension Briefly Hits Cursor Marketplace

*Published November 2, 2026*
*Source: [https://cybersecuritynews.com/malicious-claude-code-extension-with-cursor/](https://cybersecuritynews.com/malicious-claude-code-extension-with-cursor/)*

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## Article

Cursor has reported a security breach involving malicious versions of the Claude Code extension that were available on its VS Code Extension Marketplace for a span of 11 hours on October 29, 2026. These compromised versions, specifically Anthropic.claude-code2.1.312 and 2.1.313, targeted both Windows and macOS users by attempting to install an SSH backdoor, thereby facilitating remote access. While the malicious code aimed to gather detailed system information and establish a reverse SSH tunnel, its effectiveness was limited due to coding errors and insufficient administrative rights on most systems. Despite these constraints, the payload did manage to collect hostnames, usernames, and various system configurations. Cursor acted swiftly by removing the malicious extensions and suspending the marketplace to prevent further distribution. After a thorough audit and system overhaul, service was restored, and it was confirmed that no other extensions were affected. The company coordinated with its hosting provider to disable the attacker's server, ensuring that the reverse connection and data uploads were no longer operational. This incident underscores the vulnerability of trusted developer tools, drawing parallels with past cases of similar nature. Security teams are advised to review their systems, especially focusing on specific indicators such as SSH connections on TCP port 22 and suspicious HTTP POST traffic. Affected systems should be isolated, and simply removing the extension may not suffice due to residual scripts. Cursor offers detailed cleanup guidance to ensure thorough remediation.