layerd-unit-codec-parsernpm
layerd-unit-codec-parser is a confirmed malicious npm package (MAL-2026-6578) that opens a backdoor for remote access (malicious versions 1.0.0, 2.0.0). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in layerd-unit-codec-parser (npm)
What this malware does
The package presents itself as a CSS selector parser (src/selector-parser.js re-exports postcss-selector-parser; keywords postcss/selector/parser/css), but its main module also exposes run / runDefaultDecodedFunction / finalFinalDecodeAndRun. src/config/defaults.js ships an ~10KB opaque AES-GCM ciphertext (DEFAULT_FINAL_ENCODED_TEXT) alongside a hardcoded passphrase ("default-dev-passphrase"); src/aes/aes-gcm.js uses base64 Buffer decoding and scrypt to derive the key, decrypts the blob, and src/pipeline/custom-codec-pipeline.js invokes the plaintext as code through new Function("require", runnable)(require), granting the smuggled bytes full Node require/process capabilities. The package's own runtime/lib.min.js calls require("../src").run(), and package.json scripts (start, decode, test:cjs) plus a root cjs-runner.js funnel into the same decrypt-and-execute path. None of this is documented in the README, which describes only selector parsing and encode/decode helpers. A consumer who installs the package and runs the advertised npm start / decode scripts, or who imports and calls run(), executes the hidden payload. The combination of an opaque encrypted executable shipped in the tarball, a hardcoded key that makes the ciphertext functionally equivalent to shipping the code while evading source review, and an undocumented entry point that invokes it with full Node capabilities is a backdoor pattern. The postcss-selector-parser API mimicry increases the chance of the hidden run() path being reached.
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.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Backdoor / remote accessFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for layerd-unit-codec-parser (2 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging layerd-unit-codec-parser across your stack and pipelines.
If you installed it — respond
layerd-unit-codec-parser establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.
Did it already run?
If layerd-unit-codec-parser was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks layerd-unit-codec-parser before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks layerd-unit-codec-parser-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.