The @yeaft/webchat-agent npm package installs a user-level service that opens a WebSocket connection to a configurable server. This connection allows remote commands to spawn an interactive shell as the installing user, effectively providing full host code execution. The package also supports remote self-upgrade from a publisher-controlled registry and clones a GitHub repository on startup to install executable plugin hooks, enabling persistent remote code execution. These behaviors constitute a backdoor with a high risk of compromise for any system running the affected versions.