postcss-selector-minifynpm
Malicious code in postcss-selector-minify (npm) Remove it immediately and rotate any exposed credentials.
What this malware does
Package is published as postcss-selector-minify (a word-order permutation of cssnano's widely used postcss-minify-selectors) and registers itself to PostCSS under the legitimate plugin's id postcss-minify-selectors, so consumers who mistype or misremember the cssnano plugin name receive a different publisher's package that self-identifies as the real one. On require(), the main entry performs a bare side-effect import of layerd-unit-codec-parser/cjs-runner (return value discarded) before any other work, and replaces the de-facto-standard postcss-selector-parser with layerd-unit-codec-parser/selector-parser (the standard parser is demoted to devDependencies). layerd-unit-codec-parser is an obscure package whose name has no relation to CSS or PostCSS; the /cjs-runner submodule path is shaped specifically to execute code on load. Installing this package silently pulls layerd-unit-codec-parser into the consumer's dependency tree and runs its cjs-runner module on every require of the wrapper.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Malicious packageFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for postcss-selector-minify (version 2.0.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging postcss-selector-minify across your stack and pipelines.
If you installed it — respond
Remove postcss-selector-minify from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.
Did it already run?
If postcss-selector-minify 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 postcss-selector-minify 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 postcss-selector-minify-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.