# MAL-2026-5578: Malicious code in webpack-cache-clean (npm)


- **Type:** Malicious package
- **Package:** `webpack-cache-clean` (npm)
- **Published:** 11 Jun 2026
- **Also known as:** GHSA-82q4-cw9w-vjj4

## What is MAL-2026-5578?

MAL-2026-5578 is a malicious package in webpack-cache-clean, published on 11 Jun 2026. 

### Official description

On `npm install`, the package runs a postinstall hook (`node -e "require('./loader.js')"`) that spawns a detached child process. The child decodes an obfuscated base64 URL (mislabeled as 'hex' with large whitespace padding) resolving to https://jsonkeeper.com/b/L435A, an anonymous JSON paste host, performs an HTTPS GET, extracts JavaScript source from a `manifest.session` field, writes it to a temp file, and `require()`s it — with no signature, hash, or pinned-version check. The fetched code runs with the installer's privileges and can be changed by the attacker between fetches. The package metadata is also inconsistent: the package name is `webpack-cache-clean`, the README is titled `webpack-cache-plugin`, the repository URL points at `webpack-tools/webpack-cache-plugin`, and the author is the generic `Webpack Tools` — a cover story to lure installers searching for legitimate webpack cache tooling. This satisfies install-time-rce: attacker-controlled, unpinned, obfuscated remote code execution fires automatically on default install.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.

## What should I do about MAL-2026-5578?

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-2026-5578 is a malicious package: webpack-cache-clean (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-2026-5578/ (Markdown: https://insights.sbomify.com/MAL-2026-5578/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-5578

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-5578/
Summaries are generated and may contain mistakes; the official description above is the record.