MAL-2026-5579 Malicious code in webpack-cache-cycle (npm)

On npm install, package.json's postinstall hook runs node -e "require('./loader.js')". loader.js spawns a detached node process that decodes a hex-encoded URL (https://jsonkeeper.com/b/L435A — an anonymous, mutable paste host), performs an HTTPS GET, writes the response's session field to a temporary.js file, and require()s it — executing attacker-controlled JavaScript on the installer's machine. The URL is obfuscated as a hex literal padded with whitespace inside Buffer.from(...) to evade naive string scanners. The detached spawn lets npm install exit cleanly while the dropper continues asynchronously. The package's advertised purpose is a webpack cache plugin, which does not justify any network access at install time. The package name webpack-cache-cycle and README title webpack-cache-plugin impersonate legitimate webpack tooling, with placeholder author metadata (Webpack Tools) and a non-existent GitHub repository.

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.