Fake versions of the Claude Code extension on Cursor's marketplace tried to install an SSH backdoor

High Oct. 29, 2026 · Cursor

Published in edition no. 1 of Noticiário do Joãozinho · Saturday, October 31, 2026, afternoon edition

Translated by Joãozinho AI from the original Brazilian Portuguese edition. Facts, numbers and sources are the same as in the original; quotes, video titles and source names stay in their original language. Read the original in Portuguese

Versions 2.1.312 and 2.1.313 of Anthropic.claude-code for Windows and macOS, which were not made by Anthropic, were available on 10/29 between 3:27 a.m. and 2:35 p.m. MDT. They collected machine data, tried to add an attacker's SSH key and open a persistent reverse tunnel. Cursor removed the versions, took down and rebuilt the marketplace, rotated keys and took the attacker's server offline.

Why it matters It is a supply chain attack against coding agent tools. Anyone who installed or updated in that window should run Cursor's verification script and change their credentials, because uninstalling alone may not remove the persistence.

Original source: Cursor · Microsoft Security analysis — https://cursor.com/blog/claude-code-extension-security-notice

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