Threat Pulse 62High
Trojanized Claude Code extension on Cursor's marketplace planted SSH backdoors, up to 5,000 users
Severity 7ResolvedconfirmedAI and software supply chainAI-related

A tampered anthropic.claude-code v2.1.313 (Microsoft also names 2.1.312) was served from Cursor's extension marketplace on Oct 29, about 09:27 to 20:35 UTC. It ran on startup, sent host details and the names of secret-looking environment variables to the attacker, added an attacker SSH key, tried to open a reverse tunnel, and set persistence. Cursor took the marketplace down, rotated keys and says at most 5,000 users were affected. Anthropic, Microsoft and Open VSX distribution were not affected; Anthropic says its systems were not compromised.

What to do: Nov 2: Cursor confirms two affected versions, 2.1.312 and 2.1.313 (Windows and macOS). SecurityWeek and Dark Reading coverage.

· 7 days ago · cursor.com
Sourcescursor.comthehackernews.combleepingcomputer.com
On X
@cursor_aiverifiedOct 30, 07:46 UTC

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 impac

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@MsftSecIntelverifiedOct 31, 01:10 UTC

On October 29, 2026, Cursor reported that a tampered copy of Claude Code extension (anthropic.claude-code, version 2.1.313 and 2.1.312) was available and served on the Cursor extension marketplace for a few hours. https://msft.it/6019aF20x Microsoft has conf

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@cyb3ropsverifiedOct 30, 08:12 UTC

Cursor users: check your Claude Code extension. Cursor confirms a trojanized Anthropic.claude-code v2.1.313 in its extension marketplace on 29 October, 09:27 to 20:35 UTC. It estimates up to 5,000 affected users and identifies macOS ARM64 and Windows x64 buil

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@cyb3ropsverifiedOct 30, 12:06 UTC

There’s misinformation circulating about the Claude Code incident. The confirmed incident involved a tampered copy distributed through Cursor’s own marketplace. A compromise of Anthropic’s official distribution, Microsoft’s VS Code Marketplace or Open VSX has

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@TheHackersNewsverifiedOct 31, 13:48 UTC

UPDATE: Anthropic confirms its systems were NOT compromised in the Claude Code extension attack. Attackers distributed a trojanized update through Cursor's marketplace for nearly 12 hours. Official VS Code, Open VSX, and npm distributions were unaffected.

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@TheHackersNewsverifiedOct 31, 18:46 UTC

🚨 UPDATE: Cursor confirms two versions of Anthropic's Claude Code extension were affected by the SSH backdoor attack: v2.1.312 and v2.1.313 for Windows and macOS.

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Plan rubric with caps (verified sweep, Oct 31)

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