Counterfeit Claude Code extension infected up to 5,000 developers via Cursor marketplace
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.
In short
- 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.
Explained simply
Claude Code is a tool that helps developers write and work with software, and Cursor is a code editor with a marketplace for add-ons. Developers can install extensions to add features, but an extension may have access to information or systems on the computer where it runs.
A supply-chain attack happens when someone alters software or an add-on that users trust and distributes it through a usual channel. Here, the reported incident concerned a counterfeit extension listed on Cursor’s marketplace, rather than software made or published by Anthropic.
The incident matters because developers’ machines can contain project files and account details, so a malicious add-on can put more than one user at risk. It also highlights the role marketplaces and software makers play in checking extensions and responding when one is found to be unsafe.
AI Americas Celebrity Entertainment Technology World
Read the full article at the source →
Originally published by The Register as “Anthropic: That Claude Code extension compromise… couldn’t be us”.