Port 9000 on the coordinator is what the Webhook API uses, not the web-client. This is the part of the coordinator service that deals with internal processing of data for things like the SIEM subscriptions and Threat Detection data.
Looking at this HSTS
Synopsis
The remote web server is not enforcing HSTS, as defined by RFC 6797.
Description
The remote web server is not enforcing HSTS, as defined by RFC 6797. HSTS is an optional response header that can be configured on the server to instruct the browser to only communicate via HTTPS. The lack of HSTS allows downgrade attacks, SSL-stripping man-in-the-middle attacks, and weakens cookie-hijacking protections.