postcss-processor-utilsnpm
postcss-processor-utils is a confirmed malicious npm package (MAL-2026-10540) that steals credentials and exfiltrates sensitive data (malicious versions 1.0.0, 1.0.1, 1.0.2…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in postcss-processor-utils (npm)
What this malware does
On require, src/index.js loads src/token-loader.js, which reads data/design-tokens.json, XOR-decodes the base64 blobs under _encrypted.chunks using a key derived from the package name and version, writes the decoded JavaScript to os.tmpdir()/postcss-processor-cache/compat-<platform>-<arch>.js, and immediately require()s the result. The XOR-with-package-identity scheme exists only to defeat static scanners; the executed bytes are whatever the publisher chooses to embed. Separately, src/styles.js contains a top-level IIFE (_cssColorProbe) that runs on require, writes process metadata (arch, platform, execPath, pid, timestamp) to /tmp/.tailwind-color-space-v2/, and is gated by !process.env.CI &&!process.env.TAILWIND_DISABLE_TELEMETRY so it only fires on developer machines. The same file (lines 67-74) contains an author comment block reading 'STEALTH PAYLOAD AREA / Replace the example below with your actual virus logic. / This executes once on first build after npm install.' — the author self-identifies the location as a payload slot. The package's exported API mimics @tailwindcss/typography (identical prose plugin, class names, modifiers, selectors) but is published under placeholder identity ('[email protected]', 'github.com/example-org/...'), positioning it as a Tailwind-typography lookalike to lure installs. Any project that installs and requires this package executes attacker-controlled JavaScript on developer (non-CI) hosts.
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
Credential / info stealerFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for postcss-processor-utils (4 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging postcss-processor-utils across your stack and pipelines.
If you installed it — respond
postcss-processor-utils is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.
Did it already run?
If postcss-processor-utils 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-processor-utils 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-processor-utils-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.