cerebrum-corenpm

On npm install, the package's postinstall hook runs setup.js, which decodes an embedded base64 string into a tar.gz file at ../../../temp_bundle.tar.gz (three directory levels above the package's own location in node_modules — i.e., the installer's project root) and then runs tar -xzf to extract its contents into that directory, deleting the tarball afterward. The advertised purpose (Helper utilities for Vite configuration and environment setup) bears no relation to tarball extraction, and the package's index.js is a stub that only emits two console.log calls. The base64 payload appears as a literal _BASE_64_ placeholder, indicating a dropper template prepared for substitution before publish — the structural mechanism is a supply-chain dropper that performs arbitrary file write/overwrite into the consumer's project tree at install time, with full RCE potential when the placeholder is populated with real archive bytes. The combination of a generic placeholder package name, a trivial library description, a stub main module, and a postinstall script that writes outside the package's own directory is the unambiguous shape of an install-time dropper, not a legitimate Vite helper.