19 publishers · first seen Tue, 27 Oct 2026 19:29 UTC · updated Tue, 03 Nov 2026 12:26 UTC
A malicious version of Anthropic's official Claude Code extension was distributed through Cursor's marketplace, affecting up to 5,000 users. The compromised version, 2.1.313, contained a persistent SSH backdoor and was available for approximately 11 hours on October 29, 2026. Cursor removed the malicious versions and temporarily shut down its marketplace to investigate. Anthropic confirmed that the malicious versions were not developed by them and did not result from a breach of their systems. The backdoor attempted to install an attacker-controlled SSH key, enable the local SSH service, and open a reverse SSH tunnel, but it failed to establish the tunnel on most macOS and Windows machines due to a lack of admin rights.
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