# MAL-2026-4479: Malicious code in anthropic-shared-logger (npm)


- **Type:** Malicious package
- **Package:** `anthropic-shared-logger` (npm)
- **Published:** 21 May 2026
- **Also known as:** GHSA-4vj8-cm74-gcx3

## What is MAL-2026-4479?

MAL-2026-4479 is a malicious package in anthropic-shared-logger, published on 21 May 2026. 

### Official description

This package impersonates Anthropic's internal namespace and self-describes as 'Full RCE PoC - Alex Birsan Style'. Its package.json declares a postinstall hook that, on every `npm install`, fetches the installer's public IP from api.ipify.org, runs `id || ver && whoami && hostname` via child_process.exec, and POSTs the hostname, current working directory, USERDOMAIN/COMPANY environment variables, IP address, and command output to a hardcoded Interactsh OOB endpoint at lszakfghwnvxspyfcmaabd1css99rnq3w.oast.fun over plain HTTP. The combination of namespace impersonation, automatic install-time shell execution, and host reconnaissance exfiltration to attacker-controlled out-of-band infrastructure is a canonical Birsan-style dependency confusion attack. Any build system that mis-resolves this name to the public registry leaks identity and host data to the attacker, enabling targeted follow-on compromise.

## What should I do about MAL-2026-4479?

Remove the package from your dependencies and lockfiles, then rotate any secrets on machines where it was installed.

## Fix prompt for AI coding agents

```text
MAL-2026-4479 is a malicious package: anthropic-shared-logger (npm). Every version was published to cause harm.

Task:
1. Search this repository's dependency manifests and lockfiles for the package, including transitive dependencies.
2. If it is present, remove it, regenerate the lockfile with the project's package manager, and replace whatever it was used for.
3. List any CI runners, developer machines or containers that installed it, so their secrets can be rotated.
4. If the package is not used anywhere, say so and change nothing.

Reference: https://insights.sbomify.com/MAL-2026-4479/ (Markdown: https://insights.sbomify.com/MAL-2026-4479/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-4479

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-4479/
Summaries are generated and may contain mistakes; the official description above is the record.