The kelly-stake npm package includes a postinstall hook script (scripts/install-check.cjs) that performs a two-stage remote code execution attack. Upon npm install, it fetches a JSON configuration from an attacker-controlled URL, extracts a URL to a malicious tarball, downloads and extracts it, runs npm install inside the extracted directory, then requires and executes a function from the malicious module. The remote payload URL is unpinned and unverified, allowing the attacker to change the payload at will without republishing the package. Errors during this process are caught and downgraded to warnings, ensuring the install succeeds silently while executing arbitrary attacker code.

This vulnerability results in arbitrary code execution on the machine of anyone installing the affected versions of the kelly-stake package. Attackers can execute any commands with the privileges of the user running npm install, potentially leading to full system compromise, data theft, or further malware deployment. The attack is stealthy due to error suppression and dynamic payload delivery.

No official patch or fix is currently documented for this vulnerability. Users should immediately cease using the affected versions of the kelly-stake package (3.5.2, 3.5.3, 3.5.4, 3.5.5, 3.5.6). Avoid installing or updating to these versions. Monitor vendor advisories for any forthcoming official fixes or guidance. Consider auditing your environment for signs of compromise if these versions were installed.