OpenSSF/OSV advisory MAL-2026-5737 confirms this npm version as malicious. The package name impersonates the widely-used postcss-selector-parser library (which it also declares as a dependency and re-exports verbatim from src/selector-parser.js, providing cover for installers who mistype the real package). On top of that legitimate re-export, the package ships a sealed AES-GCM ciphertext as DEFAULT_FINAL_ENCODED_TEXT in src/config/defaults.js together with a hardcoded passphrase...
Source
OpenSSF Malicious Packages via OSV
Summary
Malicious code in postcss-minify-selector-parser (npm)
Details
The package name impersonates the widely-used postcss-selector-parser library (which it also declares as a dependency and re-exports verbatim from src/selector-parser.js, providing cover for installers who mistype the real package). On top of that legitimate re-export, the package ships a sealed AES-GCM ciphertext as DEFAULT_FINAL_ENCODED_TEXT in src/config/defaults.js together with a hardcoded passphrase (`default-dev-passphrase`) and salt. src/pipeline/custom-codec-pipeline.js line 53 decrypts the blob and evaluates the cleartext via `new Function("require", runnable)(require)`, handing the decrypted code full `require` capability on the installer's machine. This decode-and-eval path is reachable through the package's exported `run` / `decodeAndRunPlain` / `runDefaultDecodedFunction` API, through `require('postcss-minify-selector-parser/cjs-runner')`, and through the bundled `runtime/lib.min.js` and `scripts/cjs-runner.js`. The README documents none of this — it presents the package as a CSS selector parser. The combination of typosquat name, hidden encrypted payload, multi-layer custom codec pipeline (position-unit-codec + encode-decode-codec + AES-GCM) used solely to wrap that payload, and direct `new Function(require)` execution of the decrypted bytes is the canonical opaque-blob-eval supply-chain attack shape. Author field is empty, no repository URL is declared, license is generic ISC.
## Source: ghsa-malware (34994969794d47c784e679fd2f442e839336789f6eacec233553ee18c462e024) 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.