diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -114,6 +114,11 @@
       end
     end
 
+    # check if password is changed
+    if session[:last_password_hash] != @current_user.hashed_password
+      unauthorized_redirect 'You are forced to log out.'
+    end
+
     if GraderConfiguration.multicontests? 
       return true if @current_user.admin?
       begin