title: Most reliable way to check if user is authenticated or not in Azure AD B2C with SSO
body: <p>I am planning to use Azure AD B2C as SSO solution for 20 applications we have. 
  Question is What is the most reliable way to check if user is authenticated or not regardless of which application user is logged in. Lets say if user is logged in thorough app1 then user goes to anonymous page of app2, at client side i need to make a decision if user is logged in or not.
  I was hoping it there is a b2clogin.com endpoint where i can simple make an ajax request and check if user is logged in or not. </p>
  
  <p>Thanks in advance!</p>