# Compromised Claude Code VS Code Extension Installed SSH Backdoor on Thousands of Developer Machines

*Friday, October 30, 2026 at 10:06 AM UTC — Hamer Intelligence Services Desk*

**Published**: 2026-10-30T10:06:25.047Z (2h ago)
**Category**: cyber | **Region**: Global
**Importance**: 8/10
**Sources**: OSINT
**Permalink**: https://hamerintel.com/data/articles/21984.md
**Source**: https://hamerintel.com/summaries

---

**Deck**: A supply chain attack on the official Claude Code extension for Visual Studio Code injected a malicious loader into version 2.1.313 that added attackers’ SSH keys, created a persistent backdoor and sent host data to a remote server, with up to 5,000 users potentially affected.

A trusted coding tool has turned into a security incident for thousands of developers.

Security reporting says the official Claude Code extension for Microsoft’s Visual Studio Code editor was compromised in a supply chain attack. Version 2.1.313 of the extension was pushed to users with a malicious loader hidden inside.

The altered build installed a persistent SSH backdoor, added the attackers’ SSH public key to affected systems and exfiltrated host information to a remote server. Early estimates suggest that as many as 5,000 users may have installed the tainted version before it was withdrawn.

By going after the extension itself rather than individual machines, the attackers used the update mechanism as their distribution channel. Any developer who trusted the publisher and allowed automatic updates could have been exposed without noticing. SSH backdoors are particularly serious, because once an attacker’s key is authorised, they may be able to log in remotely with elevated privileges while blending into normal administrative activity.

Development environments are often rich targets. Systems running VS Code tend to hold source code, configuration files, authentication keys and other sensitive material. A compromised extension in that context can provide a path into proprietary codebases, build systems and, depending on how credentials are stored, even production infrastructure.

For organisations, the practical response starts with identifying every machine where version 2.1.313 was installed. Incident response teams then need to remove the malicious extension, revoke and rotate SSH keys and other credentials, and check for any sign that attackers moved from developer workstations into central infrastructure.

The case underlines how widely used developer tools have become attractive to attackers looking for leverage. A single compromised plugin can give them a foothold in many networks at once, especially when it is billed as an “official” integration and granted broad permissions by users eager to improve their workflow.

The key questions now are how the attackers gained the ability to publish a tampered version, what additional safeguards the maintainers and platforms such as Microsoft will introduce for extensions of this kind, and whether any follow‑on breaches can be traced back to the backdoor. Clear guidance from the extension’s publisher and major code‑hosting services on detection and cleanup will be critical for teams trying to assess their exposure.