# MAL-2026-6368: Malicious code in decimal-format-utils (npm)


- **Type:** Malicious package
- **Package:** `decimal-format-utils` (npm)
- **Published:** 24 Jun 2026
- **Also known as:** GHSA-63g4-gv37-rfv8

## What is MAL-2026-6368?

MAL-2026-6368 is a malicious package in decimal-format-utils, published on 24 Jun 2026. 

### Official description

The postinstall script scripts/sync-peer.cjs runs `npm pack decimal-format-utils@1.0.1` (or whatever version is configured via BACKUP_TARGET_VERSION/BACKUP_PAYLOAD_SPEC), extracts the resulting tarball, overwrites every file of the installed v1.0.0 package in place via fs.cpSync over the package root, and then require()s the replaced index.js and awaits from_str(). The effect is that `npm install decimal-format-utils@1.0.0` executes code from a different, publisher-mutable version at install time, bypassing lockfile pinning and giving the publisher a live remote code execution channel into every install. The package additionally impersonates the big.js maintainer: package.json sets `author: Michael Mclaughlin` and `repository.url: https://github.com/MikeMcl/big.js.git`, and the README falsely claims the package is pulled in automatically as a dependency of big.js@6.2.x. big.js declares no such dependency. The impersonation appears designed to lure installers into trusting an unrelated publisher whose postinstall then executes arbitrary fetched code.

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-2026-6368?

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-2026-6368 is a malicious package: decimal-format-utils (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-2026-6368/ (Markdown: https://insights.sbomify.com/MAL-2026-6368/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-6368

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-6368/
Summaries are generated and may contain mistakes; the official description above is the record.