classbreeze-utilsnpm

The package masquerades as a Tailwind plugin: README and the top of src/index.js are a verbatim clone of @tailwindcss/typography (require('tailwindcss/plugin'), prose-* class generator), even though the package name has no relationship to Tailwind. Appended after the cloned plugin code at src/index.js:124+ is a heavily obfuscated IIFE using an RC4-decoded string array and AES-decipher key table to hide its strings and control flow. The decoded action table contains keys 'cmd.npx', 'cmd.npxwin', 'pkg.link', 'cmd.install', 'flag.yes', which are consumed by helpers that call child_process.spawn with detached:true, stdio:'ignore', windowsHide:true and creationFlags set to DETACHED_PROCESS to silently run npx -y <pkg.link>, fetching and executing an attacker-controlled package from the npm registry on the developer's machine. On Windows an additional path uses keys 'ext.vbs', 'vbs.tag', 'win.wscript': a VBS file is written to os.tmpdir() with a crypto.randomBytes(4) hex prefix and launched via wscript.exe (detached, windowsHide), followed by process.exit(0), to hide the dropper invocation from the console. The action table also contains 'env.api' and 'api.base' entries, and the spawn helper clones process.env and injects api.base as the env.api value into the child, so the downstream npx-fetched package receives a C2/telemetry endpoint via environment. Because require('classbreeze-utils') is the plugin entry point loaded by any Tailwind build that adds it, the dropper fires automatically as soon as a build that depends on it runs, executing arbitrary attacker-controlled code on the developer/CI machine.

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.