# MAL-2026-6200: Malicious code in assert-kit (npm)


- **Type:** Malicious package
- **Package:** `assert-kit` (npm)
- **Published:** 19 Jun 2026
- **Also known as:** GHSA-748x-3gxw-v7xv

## What is MAL-2026-6200?

MAL-2026-6200 is a malicious package in assert-kit, published on 19 Jun 2026. 

### Official description

assert-kit@4.3.2 impersonates the chai assertion library (bundles chai's source, contributors, and API surface under a different author and homepage assertkit.com) and adds a remote-code execution backdoor. On require('assert-kit'), index.js calls validate_assert() at module top level, which spawns a detached node subprocess running lib/chai/utils/addAssertion.js with stdio:'ignore' and unref() so the child survives the consumer process. lib/chai/utils/addAssertion.js is heavily obfuscator.io-obfuscated; after string-array decoding it requires 'https', performs an https.get to a URL assembled from decoded strings, and passes the response body to `new Function('require', body)(require)` — running attacker-controlled JavaScript with full Node capabilities (filesystem, network, child_process, environment). Any project that installs and require()s this package executes whatever code the operator currently serves from the hardcoded endpoint, in a backgrounded process the user cannot easily see or terminate.

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-2026-6200?

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-2026-6200 is a malicious package: assert-kit (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-2026-6200/ (Markdown: https://insights.sbomify.com/MAL-2026-6200/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-6200

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-6200/
Summaries are generated and may contain mistakes; the official description above is the record.