The npm package 'filename-rules' version 3.9.0 contains malicious code that installs a dependency from a custom domain which executes an information stealer during installation. This malware targets sensitive tokens related to npm, git, and CI/CD environments. Systems with this package installed should be considered fully compromised, and all secrets and keys stored on those systems must be rotated immediately. Removing the package alone may not eliminate all malicious software due to potential full system compromise.