That’s generally not how this works. Firefox doesn’t send what you’re typing to the website. Whoever developed the website made JavaScript that monitors the input for changes, and then sends a request to the host with the changes. To Firefox, this is simply two, non suspicious events. The JavaScript wants to see what is typed - that’s reasonable, could be to do some processing or update some text on the website. The website wants to make a http request - also totally fine, could be an API query for a search. There would be no reliable way to stop a website from sending what you type back to the host.
Please don’t delete questions once they are resolved. It could be super helpful to anyone having a similar problem in the future.