title: Spring Security: Set GrantedAuthorities
body: <p>Is there anyway to set the <code>List&lt;GrantedAuthority&gt;</code> in the Authentication/UserDetailsImpl object? In my application, I have two layers of security, one for logging in (which uses my custom login authenticator, in the class I set the <code>Authentication</code> object using the <code>UsernamePasswordAuthenticationToken</code>) and one for a "challenge question" where the user is prompted to answer a particular question.</p>
  
  <p>What I want to do is add a <code>GrantedAuthority</code> to the current <code>List&lt;GrantedAuthority&gt;</code>, which was created during the login process, after the user answers the challenge question.</p>
  
  <p>Is this possible?</p>