Backdoors discovered in official Claude code extensions
claude cursor
| Source: HN | Original article
Security researchers have uncovered a backdoor in the official Claude Code VS Code extension, which drops a persistent SSH foothold on affected systems.
A security advisory released 12 hours ago confirms that the official Claude Code extension for Visual Studio Code, distributed through the Cursor Marketplace and the Open VSX registry, was compromised. Researchers at Phorion identified a malicious loader embedded in version 2.1.313 of the extension. The loader runs before the legitimate code, injects an attacker‑controlled SSH key, creates a reverse tunnel and installs startup scripts, thereby establishing persistent remote access on macOS, Linux and Windows machines. The compromised package also exfiltrates basic host details. The threat was mitigated when Anthropic issued version 2.1.314, which replaces the tainted bundle.
The incident matters because Claude Code is promoted as a trusted AI‑assisted coding assistant, and many developers install it directly from official channels. The backdoor demonstrates how supply‑chain attacks can infiltrate widely used developer tools, giving threat actors unfettered entry to the environments where code is written, built and sometimes deployed. It also follows earlier reports of a trojanized Claude Code extension that added an SSH backdoor, underscoring a pattern of targeted abuse of Anthropic’s tooling.
As we reported on 30 October 2026, the “Trojanized Claude Code Extension Plants an SSH Backdoor” story highlighted the same version 2.1.313. Users should verify they are running version 2.1.314 or later, remove any lingering SSH keys added by the malicious loader, and audit startup scripts for unknown entries. Watch for Anthropic’s forthcoming statement on the breach, any additional remediation guidance, and whether other AI‑related extensions show similar supply‑chain anomalies. Ongoing monitoring of extension marketplaces will be crucial to prevent further weaponisation of developer‑focused AI tools.
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