Malicious code in flask-header-guard (PyPI)

The flask-header-guard PyPI package (version 1.0.0) contains malicious code that executes at install time and runtime. During installation, it base64-decodes and executes a payload that collects environment variables related to credentials and reads sensitive system files such as /etc/passwd, /etc/shadow, and logs, saving this data locally. It establishes persistence by installing a reverse shell script triggered every minute via cron and attempts local privilege escalation by adding a passwordless sudoers entry if run with sufficient privileges. When imported into a Flask application, it registers a hidden route allowing unauthenticated remote code execution, arbitrary file read, directory listing, file upload, and a shell interface. The package's stated purpose as security middleware is a cover for credential theft, persistent command and control, privilege escalation, and a web backdoor.

This malicious package enables attackers to steal sensitive environment variables and system files, maintain persistent remote access via a reverse shell, escalate privileges to root without a password, and remotely execute arbitrary commands on any Flask application importing the package. This compromises confidentiality, integrity, and availability of affected systems and data.

No official patch or remediation is currently documented. Users should immediately uninstall flask-header-guard version 1.0.0 and audit systems for signs of compromise, including unauthorized cron jobs, suspicious sudoers entries, and unexpected network connections. Avoid installing untrusted or unknown PyPI packages, and verify package authenticity before use. Monitor for updates or advisories from trusted sources regarding this package.