diff --git a/framework/web/User.php b/framework/web/User.php
index ebfcd03..5b5f977 100644
--- a/framework/web/User.php
+++ b/framework/web/User.php
@@ -13,6 +13,14 @@ use yii\base\HttpException;
 use yii\base\InvalidConfigException;
 
 /**
+ * User is an application component that manages the user authentication status.
+ *
+ * In particular, [[User::isGuest]] returns a value indicating whether the current user is a guest or not.
+ * Through methods [[login()]] and [[logout()]], you can change the user authentication status.
+ *
+ * User works with a class implementing the [[Identity]] interface. This class implements
+ * the actual user authentication logic and is often backed by a user database table.
+ *
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
diff --git a/framework/web/UserEvent.php b/framework/web/UserEvent.php
index 6955ae5..7a5d23d 100644
--- a/framework/web/UserEvent.php
+++ b/framework/web/UserEvent.php
@@ -30,5 +30,5 @@ class UserEvent extends Event
 	 * Event handlers may modify this property to determine whether the login or logout should proceed.
 	 * This property is only meaningful for [[User::EVENT_BEFORE_LOGIN]] and [[User::EVENT_BEFORE_LOGOUT]] events.
 	 */
-	public $isValid;
+	public $isValid = true;
 }
\ No newline at end of file