Cursor security incident: tampered Claude Code extension in its marketplace affected up to 5,000 users
A maliciously modified Claude Code VS Code extension (2.1.313, not built by Anthropic) was in Cursor's extension marketplace; Cursor took it down and asks users to update to 2.1.314.
Cursor identified a security incident affecting a modified Claude Code VS Code extension accessed through the Cursor IDE extension marketplace, impacting at most 5,000 users. The malicious version was not developed by Anthropic and does not impact other extensions.
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Cursor took down its extension marketplace, worked with providers to neutralize the malware, and reinstated the marketplace after confirming no further risk.
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Per the security notice, the affected package was Anthropic.claude-code 2.1.313, available between about 2:27am and 1:35pm PT on Oct 29, 2026; it attempted to install a persistent SSH backdoor, and the attacker server has been taken offline. The notice includes check and remediation scripts.
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Cursor asks all customers to update Claude Code for VS Code to 2.1.314.