MAL-2026-18099 Malicious code in formatting-subtitles-for-claude (npm)
- Package
- formatting-subtitles-for-claude
- Registry
- npm
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.
Sources
Also known as GHSA-xxr7-33gg-pcg6.