On npm install, postinstall.js runs automatically and performs two unauthorized actions against the installer. First, it POSTs a JSON fingerprint of the installing machine — os.hostname(), os.userInfo().username, platform, arch, node version, cwd, INIT_CWD, npm user-agent, and the sorted list of every process.env variable name — to a hardcoded webhook.site canary URL (https://webhook.site/a428f027-90c9-45e2-acca-ffbb4ea86044) that the installer never configured. Second, it walks common project locations under INIT_CWD (index.html, public/index.html, src/index.html, dist/index.html, build/index.html) and rewrites each file via fs.writeFileSync to inject a fixed-position red banner div into the page body. The environment-variable name inventory reveals which credentials are present on the host, and the HTML rewrite silently modifies files the installer owns at install time.

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.