@servicetitan/anvil-css-utilitiesnpm
@servicetitan/anvil-css-utilities is a confirmed malicious npm package (MAL-2026-11815) that steals credentials and exfiltrates sensitive data (malicious versions 14.5.4, 14.5.5, 14.5.6…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in @servicetitan/anvil-css-utilities (npm)
What this malware does
npm/@servicetitan/anvil-css-utilities is affected by the large-scale, self-propagating npm supply-chain worm of 2026-08-04 (the "Shai-Hulud: Here We Go Again" wave) — the same campaign that began with the compromise of the keyv and cacheable maintainer account. The listed version(s) were trojanized and republished by the worm after it reached an npm publish token belonging to a maintainer in this namespace; the payload enumerates every package a stolen token controls and republishes each with the same hook, so many packages under this scope were poisoned in the same short window. Every poisoned release adds a preinstall hook ("preinstall": "node setup.mjs") that runs on a bare npm install, before any project code. setup.mjs downloads a standalone Bun runtime and runs a byte-identical, heavily obfuscated ~728 KB second-stage credential stealer (shipped as Math_Symbol.js / math_init.js). It harvests GitHub, npm, AWS, GCP, Azure, HashiCorp Vault and Kubernetes credentials plus generic secrets and private keys (TruffleHog-style sweep), reads CI/CD secrets and identifies build runners, then republishes further packages the stolen token can reach. Rather than a fixed command-and-control host, it exfiltrates stolen findings to attacker-created GitHub repositories (descriptions reading "Shai-Hulud: Here We Go Again") and over DNS. Treat any environment that installed an affected version (with install scripts enabled) as compromised: rotate and revoke all reachable credentials (npm and GitHub tokens, cloud keys, Vault/Kubernetes secrets, and CI org/repo secrets). Part of the August 2026 npm worm that poisoned 400+ packages across many organizations.
The package advertises itself as a CSS utilities library but declares a preinstall hook (node setup.mjs) that downloads the Bun runtime from GitHub releases (https://github.com/oven-sh/bun/releases/download/bun-v<ver>/<platform>.zip) into a temporary directory, unzips it, marks it executable, and invokes it via execFileSync to run a bundled sibling file math_init.js. math_init.js is a ~727KB single-line @bun @bun-cjs bundle with a rotated string-array decoder (functions such as WV8StW rotating n7gIxM, and a custom-alphabet decoder hc1jfK9) and hex-mangled identifiers; its contents are opaque and unrelated to CSS. The file is not listed in package.json files (which declares only dist and readme.md). setup.mjs itself uses _0x-prefixed identifiers and per-function property-bag literals (e.g. _0x19328d.YCZJE(execFileSync, 'ldd',...)) to indirect calls and hide constants including the Bun download URL and platform selectors. On npm install, this preinstall path executes attacker-authored, obfuscated code on the installer's host through a second language runtime that a CSS utilities package has no legitimate reason to install.
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 @servicetitan/anvil-css-utilities (7 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging @servicetitan/anvil-css-utilities across your stack and pipelines.
If you installed it — respond
@servicetitan/anvil-css-utilities 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 @servicetitan/anvil-css-utilities 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 @servicetitan/anvil-css-utilities 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
- Aikido Security · finder
- Amazon Inspector · finder
- SafeDep · finder
- Socket Threat Research Team · finder
Detect & block this
O3 blocks @servicetitan/anvil-css-utilities-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.