I setup openfire 3.6.0 and webchat 4.0.0 (all latest versions). In Form UI username field has a “Populate with user’s previous choice.” option selected. Web authentication option enabled too.
So, when a user login via web form a first time - all OK. But, when user visit login page again - he has a filled username filed. But this username in quotes! Of course, user can’t login, because username incorrect. In next login try user got username with two quotes before and after text, etc.
I looked into source of HTML page and see code like this: