Malicious Claude Code extension hit Cursor: 5,000 at risk

Cursor, the AI coding company now owned by SpaceX, disclosed the incident on Friday.Anthropic didn't build the extension.

Someone modified it with malicious code, and it stayed live from about 2:27am PT to 1:35pm PT.It targeted basic information about your computer, such as hostname, username, operating system, and public IP address.

All of these pieces of information help the attacker identify your identity and position within the network.It attempted to enable remote control for the attacker.

According to Cursor, one of the steps involved administrator permissions, and hence, it was bound to fail on most computers.After the detection of the browser extension, Cursor deployed the malicious version of it and stopped its dissemination.

It also shut down the whole marketplace for good measure.The company rebuilt the marketplace and brought it back online.

It says no other extension was affected.Are you affected?

What to check in CursorIn case you have installed an extension for Claude Code via Cursor’s Marketplace on Thursday, be sure to take a look at the publisher of that extension and remove any parts not from Anthropic.

It seems that Cursor has not stated how it will alert the affected users yet.In a case from 2025, a fake extension for Solidity from the Open VSX marketplace was used by hackers to steal $500,000 worth of cryptocurrencies from a security-aware developer.

Extensions have your permission to run and are easy to install for developers.

Malicious Claude Code extension hit Cursor: 5,000 at risk October 30, 2026.