Cursor says modified Claude Code extension hit up to 5,000 users
Cursor says a modified Claude Code extension on its marketplace affected up to 5,000 users. Anthropic did not build it, and the marketplace is back.
Cursor says a modified copy of the Claude Code extension for VS Code, accessed through its Cursor IDE extension marketplace, caused a security incident affecting at most 5,000 users. The company announced it on X today.
"This malicious version of the extension was not developed by Anthropic," Cursor wrote. It adds that the incident does not touch other marketplace extensions, Grok Bot, Grok or its other SpaceXSI products.
The response, per Cursor: it took the marketplace down this afternoon, worked with relevant providers to neutralize the malware, and reinstated the marketplace after confirming there was no further risk. Affected users are pointed to a blog post with instructions for finding the malicious package and mitigating any impact. Cursor is also asking all customers to update to Claude Code for VS Code version 2.1.314.
What the notice leaves out is considerable. It does not say who uploaded the modified extension, when it first appeared, how long it was available, or what the malware did on affected machines, including whether any data left them.
My take: "at most 5,000" is a ceiling, not a count, and a ceiling is not an impact assessment. The word "modified" carries the story. The extension wore a trusted name, which is the whole trick, and a marketplace that lists a name is vouching for it whether it intends to or not. Until the post-mortem arrives, the open questions outnumber the answers.
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Sources
Meanwhile at the anchor desk
A marketplace pulled and then restored, and the word "SpaceXSI" casually dropped into the notice: the drama, the speed, the empire. Even the incident response has a corporate universe attached.
If you run Claude Code in VS Code, update to 2.1.314 and read the notice at cursor.com/blog/claude-code-extension-security-notice to check for the malicious package. Pin your extension sources while you're at it.
