Stuck On Secure Spring Developer (Beginner) URL Parameters Challenge

The lab is around trying to mediate a vulnerability by changing a GET request to a POST request in order to keep sensitive login information out of the URL params. But basically I don't know how I need to go about changing the code(apart from changing "GET" to "POST" on the login form and in a backend method). I'm at a total loss on this one so I'd really appreciate some guidance or an example. I wasn't sure if I should also be making changes to the mapping on the controller (although this isn't mentioned in the lab).

These are the changes I have made so far

 <form th:action="@{/login}" method="POST">

    protected LoginProcessingFilter(AuthenticationManager authenticationManager) {
      super(new AntPathRequestMatcher("/login", "POST"));
      setAuthenticationManager(authenticationManager);
      setAuthenticationSuccessHandler(new SimpleUrlAuthenticationSuccessHandler("/home"));
    }

Thanks in advance for any assistance