The layerd-unit-codec-parser npm package (version 1.0.0) presents itself as a CSS selector parser but contains a concealed malicious payload. The package includes an approximately 10KB AES-GCM encrypted ciphertext alongside a hardcoded passphrase ('default-dev-passphrase'). At runtime, the ciphertext is decrypted using scrypt-derived keys and base64 decoding, then executed dynamically via new Function with full access to Node.js require and process capabilities. This hidden code execution path is accessible through npm scripts (start, decode, test:cjs) and an undocumented run() function. The package's README does not disclose this behavior, and the API mimics a legitimate selector parser, increasing the likelihood of the malicious code being executed unintentionally. This constitutes a backdoor allowing arbitrary code execution in the context of the host environment.

If a user installs and runs the layerd-unit-codec-parser package version 1.0.0 and executes the npm start or decode scripts, or calls the run() function, the hidden malicious payload will execute with full Node.js capabilities. This can lead to arbitrary code execution, potentially compromising the host system, stealing data, or performing other malicious actions. The presence of a hardcoded decryption key and encrypted payload bypasses typical source code review defenses, making detection difficult. There are no known exploits in the wild reported at this time.

No official patch or remediation is currently available for this malicious package. Users should avoid installing or using layerd-unit-codec-parser version 1.0.0. Since this is a malicious package published to npm, the best mitigation is to remove it from any projects and replace it with a trusted alternative. Monitor package sources carefully and verify package integrity before use. Check the npm registry and vendor advisories for any updates or removals related to this package.