---
id: "GHSA-xxr7-33gg-pcg6"
kind: "package"
aliases: ["GHSA-xxr7-33gg-pcg6", "MAL-2026-18099"]
title: "Malicious code in formatting-subtitles-for-claude (npm)"
severity: "critical"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "formatting-subtitles-for-claude", "fixed": [], "affected": "all versions", "ecosystem": "npm"}]
ecosystems: ["npm"]
tags: ["malicious", "package"]
not_affected_if: []
published_at: "2026-10-20T15:59:30+00:00"
first_seen_at: "2026-10-26T20:51:55+00:00"
updated_at: "2026-10-26T21:05:48+00:00"
sources: [{"source": "osv-malicious", "url": "https://osv.dev/vulnerability/MAL-2026-18099", "first_seen_at": "2026-10-26T20:51:55+00:00"}]
---

# Malicious code in formatting-subtitles-for-claude (npm)

## Affected

- npm:formatting-subtitles-for-claude affected all versions fixed ?

## Timeline

- 2026-10-26T20:51:55+00:00 osv-malicious https://osv.dev/vulnerability/MAL-2026-18099

## From the sources

---
_-= Per source details. Do not edit below this line.=-_

## Source: amazon-inspector (f683c00ef9c42d55e37cdb367179f21e58ce2441dba55485d6d19670bcefa700)
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.

## Source: ghsa-malware (df3e538de57455a661949a30ffd71da5534d5f36c59147155be0b957d9e427df)
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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_