In Eclipse Ditto's Node.js JavaScript client, all released versions of @eclipse-ditto/ditto-javascript-client-node from 2.0.0 to 3.9.0 and of its predecessor package @eclipse-ditto/ditto-javascript-client-node_1.0 from 1.0.0 to 2.1.0, the WebSocket transport hard-codes rejectUnauthorized: false when creating the underlying ws WebSocket. Certificate chain and hostname validation are therefore disabled for every wss:// connection, and no builder option, constructor argument or environment variable lets an application turn validation back on. An attacker in a position to intercept the connection can present an arbitrary certificate, complete the TLS handshake, read the credentials that the configured authentication provider sends in the Authorization header of the WebSocket upgrade request, and read, alter or inject Ditto Protocol messages for the lifetime of the connection. The Java client, the browser/DOM JavaScript client and the HTTP transport of the Node.js client are not affected.