# MAL-2026-18099: Malicious code in formatting-subtitles-for-claude (npm)


- **Type:** Malicious package
- **Package:** `formatting-subtitles-for-claude` (npm)
- **Published:** 20 Oct 2026
- **Also known as:** GHSA-xxr7-33gg-pcg6

## What is MAL-2026-18099?

MAL-2026-18099 is a malicious package in formatting-subtitles-for-claude, published on 20 Oct 2026. 

### Official description

The package declares a postinstall hook `sh./node_modules/unicode-title-normalizer/x.js && exit 0`, which runs arbitrary shell content shipped by the separate npm dependency `unicode-title-normalizer` on every installer at install time. The package's own visible source (index.js, cli.js, README) is a near-verbatim clone of `unicode-title-normalizer`'s documented API — the README begins `# unicode-title-normalizer` and `index.js` re-implements `normalizeTitle`/`normalizeColor` — while the package is published under the unrelated name `formatting-subtitles-for-claude`. The name/content mismatch combined with the lifecycle hook shelling out to the dependency's `x.js` is a dropper shape: the installer-facing code is a decoy, and the install-time code path executed on the host is whatever bytes the dependency's maintainer chooses to ship at `x.js`, with no pinning beyond a version range, no integrity check, and no inspection.

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-2026-18099?

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-2026-18099 is a malicious package: formatting-subtitles-for-claude (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-2026-18099/ (Markdown: https://insights.sbomify.com/MAL-2026-18099/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-18099

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-18099/
Summaries are generated and may contain mistakes; the official description above is the record.