Security notice — malicious version of Anthropic.claude-code (2.1.313) identified in the Cursor Extension Marketplace

Cursor reported that a malicious, unauthorized build of the Anthropic Claude Code extension, version 2.1.313, was available in its VS Code extension Marketplace between 2:27 a.m. and 1:35 p.m. PT on October 29, 2026, potentially affecting up to 5,000 users. The package gathered system and user details, added an attacker-controlled SSH key, attempted to enable SSH and establish a persistent reverse tunnel, and sent host information to an attacker-operated server, although administrative-permission requirements and coding errors meant the most serious access attempts would usually fail. Cursor removed the extension, temporarily shut down and rebuilt the marketplace, audited other extensions, rotated keys, and coordinated with the hosting provider to disable the attacker’s server. Users who installed or updated the affected version are advised to check for the “svc-telemetry” SSH key and other indicators, isolate affected devices, remove persistence mechanisms and tunnel processes using provided remediation scripts, and rotate credentials and sessions because uninstalling the extension alone may not remove standalone malicious components.

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