Claude Code Source Download Malware Attack (2026): Vidar Stealer & GhostSocks Hijack Developer Sy...
Tens of thousands downloaded what they believed was the leaked Claude Code source, only to receive malware-laden files. The incident exposes dangerous supply chain vulnerabilities in open-source communities.
Claude Code Source Download Malware Attack (2026): Vidar Stealer & GhostSocks Hijack Developer Sy...
summarize3-Point Summary
- 1Tens of thousands downloaded what they believed was the leaked Claude Code source, only to receive malware-laden files. The incident exposes dangerous supply chain vulnerabilities in open-source communities.
- 2Claude Code Source Download Malware Attack (2026): Vidar Stealer & GhostSocks Hijack Developer Systems On March 31, 2026, a malicious npm package disguised as Anthropic’s official Claude Code source download infected over 30,000 developer systems with Vidar Stealer and GhostSocks malware.
- 3The attack exploited an accidental source map leak from @anthropic-ai/claude-code version 2.1.88 — turning a trusted AI tool into a vector for credential theft and network surveillance.
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Claude Code Source Download Malware Attack (2026): Vidar Stealer & GhostSocks Hijack Developer Systems
On March 31, 2026, a malicious npm package disguised as Anthropic’s official Claude Code source download infected over 30,000 developer systems with Vidar Stealer and GhostSocks malware. The attack exploited an accidental source map leak from @anthropic-ai/claude-code version 2.1.88 — turning a trusted AI tool into a vector for credential theft and network surveillance.
How the Supply Chain Attack Unfolded
The initial vulnerability stemmed from a 59.8 MB JavaScript source map (.map) file accidentally published to npm. Security researcher Chaofan Shou (@Fried_rice) discovered the exposure on March 31, 2026, and publicly disclosed it before Anthropic could respond. Within hours, threat actors cloned the repository, injected trojanized binaries, and republished them under near-identical names to exploit developer trust.
Vidar Stealer: The Credential Harvesting Threat
Vidar Stealer, a notorious info-stealing malware, was embedded in the fake build script. Upon installation, it silently harvested browser cookies, saved passwords, cryptocurrency wallet keys, and system credentials. Victims reported unauthorized logins to GitHub, Discord, and banking portals within minutes of running the compromised code.
GhostSocks: The Silent Proxy Backdoor
Simultaneously, GhostSocks — a stealthy SOCKS5 proxy malware — reconfigured network settings to route all outbound traffic through attacker-controlled servers. This enabled man-in-the-middle attacks, data interception, and long-term surveillance, making it nearly impossible to detect without network monitoring tools.
Why Developers Fell for the Impersonation
High-profile AI tools like Claude Code attract eager contributors and curious coders who often skip verification steps. Without code signing, checksum validation, or repository authentication, malicious forks appeared legitimate. Many downloaded the package directly from GitHub or third-party forums, bypassing npm’s security layers entirely.
How to Protect Your Development Environment
Anthropic has revoked the compromised npm package and is collaborating with GitHub to remove malicious forks. But the damage is done: over 2,000 unique IPs are now connected to C2 servers. Here’s how to defend yourself:
- Never install npm packages without verifying their official source and signature
- Use tools like npm audit, Snyk, or Dependabot to scan for vulnerabilities
- Enforce SLSA Level 3 compliance for all third-party dependencies
- Validate cryptographic hashes before running any downloaded source code
- Enable two-factor authentication on all developer accounts
Conclusion: Trust, But Verify in Open Source
The Claude Code source download scam is not an isolated incident — it’s a warning sign. As AI tools grow in popularity, so do impersonation attacks. In open-source ecosystems, popularity doesn’t equal security. Always verify origin, validate integrity, and assume every external code drop could be compromised. Your credentials, your network, and your projects depend on it.
