Zendesk provide script for their chat widget. But the script can easily be copied by anyone who use our website. How do we ensure that widget is secured and only authenticated users can chat.
It looks like you can define domains or IP addresses where the widget can load in the Zendesk Chat Dashboard. See this article for more details - https://chat.zendesk.com/hc/en-us/articles/219848967-Restricting-the-Chat-widget-by-country-or-domain
Beyond that, you can require that users sign in to the chat widget as explained here - https://chat.zendesk.com/hc/en-us/articles/360002037187-Authenticating-users-in-Chat, or you can build it in to your website as well.