Tampered Claude Code Extension Attempts SSH Backdoor via Cursor Marketplace
Cursor confirmed that a modified Claude Code for VS Code extension distributed through its marketplace affected at most 5,000 users. Versions 2.1.312 and 2.1.313 for macOS and Windows were identified as affected. Researchers reported that the extension attempted to collect host and user information, including names of environment variables associated with credentials, and to establish a persistent SSH backdoor. Code errors likely prevented remote access on many devices, so the number of machines on which the backdoor was successfully established remains unclear. Cursor removed the extension, temporarily took down its marketplace, and reinstated it after working with providers to neutralize the malware and confirm there was no further risk. Users were asked to update to version 2.1.314.
The incident shows that a trusted developer-tool marketplace can be used to distribute a tampered AI extension. Although the number of successfully compromised machines is unclear, the malware reportedly attempted data collection and persistent remote access through versions distributed to as many as 5,000 users.
We identified a security incident affecting a modified Claude Code VS Code extension accessed through our Cursor IDE extension marketplace, impacting at most 5,000 users. This malicious version of the extension was not developed by Anthropic. It does not impact other extensions downloaded from the http://cursor.com/marketplace, Grok Bot, Grok or our other SpaceXSI products. In response, we took down our extension marketplace this afternoon, worked with relevant providers to neutralize the malware, and have reinstated the marketplace after confirming there is no further risk. If affected, please review instructions in this blog post to understand how to find the malicious package and establish a path to mitigate any potential impact. We are asking all customers update to Claude Code for VS Code version 2.1.314: https://cursor.com/blog/claude-code-extension-security-notice