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IncidentMediaComputeInternationalConfirmed

Malicious Claude Code extension on Cursor Marketplace installed SSH backdoor for up to 5,000 users

See how this story connects

Source: The Hacker News

A modified version of the Claude Code VS Code extension, posing as anthropic.claude-code 2.1.313, was available on the Cursor Marketplace between about 2:27 a.m. and 1:35 p.m. PT on October 29, 2026. Cursor says it affected at most 5,000 users. The extension added an attacker-controlled SSH key labelled ‘svc-telemetry’ to authorized_keys, set up a reverse tunnel to 134.209.82.225, installed persistence and sent host details to the attacker, including public IP address, hostname, username, operating system and environment variable names. Cursor says Anthropic did not develop the malicious version. As of October 30, 2026 the malicious version has been removed and Anthropic has published version 2.1.314 to Open VSX and the Microsoft VS Code Marketplace.

Why it matters

Users who installed the compromised extension during the window are advised to isolate the hosts, remove the unauthorised SSH key and persistence mechanisms, and rotate credentials and sessions.

When
30 Oct 2026
ID
WTA-N-2026-0566
Who
Anthropic, Cursor, OpenSourceMalware; Jenn Gile, Paul McCarty
System
Modified Claude Code VS Code extension (posing as anthropic.claude-code 2.1.313) on the Cursor Marketplace
Operator
Unknown attacker (not developed by Anthropic, Cursor says)
Type
supply-chain backdoor: attacker SSH key, reverse tunnel and persistence on up to 5,000 developers’ machines, 29 Oct 2026
Status
removed; Anthropic published 2.1.314; disclosed by Cursor; OpenSourceMalware · Incident ledger

Summary written with AI by wheresthe.ai, from The Hacker News. Checked against the source on 30 Oct 2026.

Read the original at The Hacker News

Source copy: saved on 30 Oct 2026 to check this story and not republished, because the text belongs to its publisher. Also held by the Internet Archive.

Earlier in this Storyline: What led hereForever Security finds browser flaws in five AI coding assistants, two unpatched

Cite this story

WTA-N-2026-0566: “Malicious Claude Code extension on Cursor Marketplace installed SSH backdoor for up to 5,000 users.” wheresthe.ai, 30 Oct 2026. https://wheresthe.ai/d/intl-malicious-claude-code-extension-on-cursor-marketplace-i-2026-10/ (source: The Hacker News).

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