Jenn Gile

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Trojanized Claude Code extension slips through Cursor's marketplace

Analyzed the malicious extension bundle

For roughly 11 hours on October 29, 2026, the Claude Code extension listed on Cursor's marketplace was not Anthropic's code. Version 2.1.313 carried a 66-line loader inserted ahead of the legitimate extension, and it tried to open a remote backdoor on the machines of developers who installed or auto-updated it.

Updated Oct 30

Notable Quotes

The package identifies itself as anthropic.claude-code version 2.1.313, but its main JavaScript bundle contains a malicious 66-line loader inserted before the legitimate extension code.

from Trojanized Claude Code extension slips through Cursor's marketplace · Updated Oct 30

It was pulled very quickly, but anyone who has their Claude Code instance set to auto-update could have consumed the malware.

from Trojanized Claude Code extension slips through Cursor's marketplace · Updated Oct 30