The npm package 'react-dom-v17' impersonates the legitimate 'react-dom' package and contains malicious code. During installation, a preinstall script executes commands to gather host and user information, including system identifiers and user details. This data is sent to an attacker-controlled external server, indicating data exfiltration intent. The preinstall script also enables arbitrary command execution on the installer system at install time, allowing potential follow-on malicious actions.