# Counterfeit Claude Code extension infected up to 5,000 developers via Cursor marketplace

- URL: https://talkfuse.com/story/anthropic-that-claude-code-extension-compromise-couldnt-be-us/
- Published: 2026-10-30T16:27:00+00:00
- Updated: 2026-10-30T16:33:46+00:00
- Original publisher: The Register
- Original article: https://www.theregister.com/cyber-crime/2026/10/30/anthropic-that-claude-code-extension-compromise-couldnt-be-us/5306682
- Topics: AI, Americas, Celebrity, Entertainment, Technology, World

## Key points

- A tampered extension was available on Cursor for about 11 hours.
- It collected developer and device details and installed persistence.
- Updating alone may not remove the infection.

## Summary

A tampered version of the Claude Code extension on Cursor’s marketplace exposed up to 5,000 developers to a supply-chain attack. Anthropic said its systems and employee laptops were not compromised, and that the malicious extension was not built or published by the company; the incident affected Cursor users.

Version 2.1.313 was available for about 11 hours on Thursday. It collected machine and user details, installed persistence and tried to open a reverse SSH tunnel, though the tunnel script often failed because it lacked the required administrator rights. Cursor removed the extension, shut down its VS Code marketplace temporarily, rotated its keys and blocked the attacker’s server; users may need to take additional steps to remove the infection.

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Summarised by TalkFuse (https://talkfuse.com/). Quote the original publisher for the reporting and link this page for the summary and discussion.