StarterSTS can create a single-sign-on session with the user. This allows the client to use multiple web applications without getting asked for credentials again.
This is a feature you might want - or not. But there are also several ways to customize it.
StarterSTS uses the ASP.NET forms authentication infrastructure to create and maintain a SSO session. The settings (especially the default timeout of 300 minutes) can be changed in web.config
<authentication
mode="Forms">
<forms
name=".STARTERSTSAUTH"
requireSSL="true"
defaultUrl="~/default.aspx"
loginUrl="~/login.aspx"
cookieless="UseCookies"
slidingExpiration="false"
timeout="300" />
</authentication>
StarterSTS allows to insert a confirmation screen in every logon process. This way a user is notified when he logs into an relying part. This can help to fight CSRF attacks.
You can enable the confirmation screen by setting the requireLoginConfirmation attribute in starterSTS.config to true.
To remove the SSO feature alltogether, set the DisplayRememberMe attribute on the login control at ~/login.aspx to false.