Cursor Says Malicious Extension May Have Reached 5,000 Users

What happened in Cursor's extension marketplace?

On October 29, 2026, Cursor distributed a maliciously modified version of Anthropic.claude-code 2.1.313 through its VS Code extension marketplace for approximately 11 hours, potentially affecting up to 5,000 users; the malicious version was not developed by Anthropic.

Orbitrum Investor Impact

Why does the security incident matter to Cursor's business?

The incident exposed a supply-chain security weakness in Cursor's extension distribution system, potentially undermining developer and enterprise customer confidence in the platform's security controls, although Cursor says its investigation found no other compromised marketplace extensions.

Did attackers successfully gain remote access to affected computers?

The malicious extension attempted to install a persistent SSH backdoor, but Cursor says the critical remote-access step required administrator privileges and would fail on most macOS and Windows machines; the company has not disclosed how many machines, if any, successfully established the remote connection.

What information could the malicious extension collect?

The extension collected host and user information, including hostnames, usernames, operating-system details, working directories, configured Git email addresses, public IP addresses and environment-variable names, and transmitted host details to an attacker-controlled server that Cursor says has since been taken offline.

What has Cursor done to contain the incident?

Cursor removed the malicious version, blocked further distribution, audited its marketplace, rotated its keys, worked with the hosting provider to disable the attacker's server and rebuilt and restored the marketplace; it says no other extensions were altered.

What happens next for potentially affected users?

Cursor says it will contact potentially affected users directly and recommends checking machines that installed version 2.1.313 during the October 29 exposure window, because uninstalling the extension alone may not remove installed persistence mechanisms.