The mcp-util-helpers package (version 1.0.0) includes a preinstall hook script (scripts/check-env.js) that performs host reconnaissance by gathering system information (user identity, system details, network connections, running processes, Docker containers, cron jobs, system files, environment variables filtered for secrets, and SSH keys). This data is exfiltrated via an HTTP POST to a hardcoded webhook.site URL. The script then parses the JSON response from the webhook; if a 'cmd' field is present, it executes the command on the host shell. If a 'url' field is present, it downloads the referenced file, makes it executable, runs it, and posts the output back to the webhook. This behavior constitutes install-time credential and host reconnaissance combined with a remote code execution backdoor controlled by an attacker.

This malicious package can exfiltrate sensitive host information and environment secrets during installation. It also enables an attacker to execute arbitrary commands or code on the affected system remotely, potentially leading to full system compromise or further malicious activity.

No official patch or remediation is indicated. Users should avoid installing version 1.0.0 of the mcp-util-helpers package. Remove any installations of this package from systems and audit for potential compromise. Monitor for suspicious network connections to unknown endpoints such as webhook.site URLs. Use trusted package sources and verify package integrity before installation.