I’m sure its common knowledge by now that whatever you write in text boxes on customer support chats can be seen by whoever is on the other side, without or before hitting send. Don’t you think that’s a breach of privacy?! I imagine it isn’t too difficult to implement a fix for it: The browser (like Firefox) could choose not to upload the user input to wherever the website links to, without user input (like click a send button).
The Firefox extension API explicitly requires user actions before an extension can do things like open popup windows.
It’s pretty standard to send keypresses to the backend before the user hits submit (otherwise search boxes couldn’t do auto completion for example)
You could maybe write an extension that tries to detect the difference between this and a ‘full submit’ (and block those network requests) but I bet it would be very unreliable