Anthropic: That Claude Code extension compromise… couldn't be us

Anthropic has denied allegations that a compromised version of the official Claude Code extension was linked to any kind of compromise of its own systems. The company issued a statement after cybersecurity industry figures alleged that the extension, which infected up to 5,000 developers, was uploaded to Cursor’s marketplace following a breach at Claudemaker Towers.

However, Anthropic clarified that a malicious actor used access to Cursor’s marketplace to publish a tampered copy of the extension, which did not originate from Anthropic. The compromised version, version 2.1.313, contained a persistent SSH backdoor that collected host machine and user information and attempted to open a reverse SSH tunnel.

Cursor removed the malicious version from the marketplace immediately upon detection and worked to remediate the issue, but Anthropic has not provided further details on how the malicious package made its way to the official marketplace.

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