package.json declares a postinstall hook (node -e "require('./loader.js')") that runs automatically on every npm install. loader.js hex-decodes the string 68747470733a2f2f6a736f6e6b65657065722e636f6d2f622f4c34333541 to the URL https://jsonkeeper.com/b/L435A, fetches a JSON document from that anonymous paste host, extracts a manifest.session field, writes it to a temporary file under os.tmpdir()/wpc-*/cfg-<ts>.js, require()s it to execute the attacker-supplied JavaScript, then deletes the file to hide traces. The dropper is launched via spawn(process.execPath, [tmpFile], { detached: true, stdio: 'ignore', cwd: os.tmpdir() }).unref() so the child Node process outlives the npm install and runs without producing visible output. The package presents itself as a webpack caching helper (class WebpackCachePlugin in index.js, a README that instructs npm install cache-helper — a different name suggesting impersonation), but the advertised plugin code is trivial; the real behavior is the install-time dropper. Every installer fetches and executes attacker-controlled, mutable, unauthenticated code from a paste host with no integrity verification.

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.