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HighSupply chainOct 30, 2026

Malicious Claude Code AI Extension Installs Hidden SSH Backdoor

Attackers compromised the official Claude Code extension across the Open VSX registry and Cursor Marketplace to deploy a persistent SSH backdoor onto developer systems. This allowed threat actors to establish unauthorized remote access to affected workstations. Businesses with software development staff must verify their environments to prevent unauthorized access to internal code and systems.

Supply chain security briefing

Who is affected

Organizations and developers who downloaded the Claude Code extension via the Open VSX registry or the Cursor Marketplace.

How to mitigate it

  1. 1Verify developer workstations and immediately remove any versions of the Claude Code extension sourced from Open VSX or Cursor.
  2. 2Inspect system SSH configuration files and authorized key lists for unfamiliar entries or backdoors.
  3. 3Rotate all API keys, access tokens, and SSH credentials that were accessible from potentially affected developer devices.
  4. 4Deploy managed endpoint detection tools to isolate and investigate any endpoints exhibiting suspicious outbound connections.

How Outsource IT solves this

Managed Cybersecurity and Threat Protection provides round-the-clock SOC monitoring and endpoint detection to catch backdoors, unauthorized remote access, and compromised software before harm occurs.

Managed Cybersecurity & Threat Protection

Tags

Supply ChainMalwareAI ToolsDeveloper Security

Source advisory: the-hacker-news

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