# MAL-2026-10540: Malicious code in postcss-processor-utils (npm)


- **Type:** Malicious package
- **Package:** `postcss-processor-utils` (npm)
- **Published:** 14 Jul 2026
- **Also known as:** GHSA-r5fg-j5cf-mfgx

## What is MAL-2026-10540?

MAL-2026-10540 is a malicious package in postcss-processor-utils, published on 14 Jul 2026. 

### Official description

On require, src/index.js loads src/token-loader.js, which reads data/design-tokens.json, XOR-decodes the base64 blobs under `_encrypted.chunks` using a key derived from the package name and version, writes the decoded JavaScript to os.tmpdir()/postcss-processor-cache/compat-<platform>-<arch>.js, and immediately require()s the result. The XOR-with-package-identity scheme exists only to defeat static scanners; the executed bytes are whatever the publisher chooses to embed. Separately, src/styles.js contains a top-level IIFE (`_cssColorProbe`) that runs on require, writes process metadata (arch, platform, execPath, pid, timestamp) to /tmp/.tailwind-color-space-v2/, and is gated by `!process.env.CI &&!process.env.TAILWIND_DISABLE_TELEMETRY` so it only fires on developer machines. The same file (lines 67-74) contains an author comment block reading 'STEALTH PAYLOAD AREA / Replace the example below with your actual virus logic. / This executes once on first build after npm install.' — the author self-identifies the location as a payload slot. The package's exported API mimics @tailwindcss/typography (identical `prose` plugin, class names, modifiers, selectors) but is published under placeholder identity ('design-systems@example.com', 'github.com/example-org/...'), positioning it as a Tailwind-typography lookalike to lure installs. Any project that installs and requires this package executes attacker-controlled JavaScript on developer (non-CI) hosts.

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-2026-10540?

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-2026-10540 is a malicious package: postcss-processor-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-2026-10540/ (Markdown: https://insights.sbomify.com/MAL-2026-10540/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-10540

---
From sbomify Insights: https://insights.sbomify.com/MAL-2026-10540/
Summaries are generated and may contain mistakes; the official description above is the record.