diff --git a/docs/guide/rest.md b/docs/guide/rest.md
index 3bd341d626..6b434482b0 100644
--- a/docs/guide/rest.md
+++ b/docs/guide/rest.md
@@ -657,8 +657,7 @@ After a user is authenticated, you probably want to check if he has the permissi
 action for the requested resource. This process is called *authorization* which is covered in detail in
 the [Authorization chapter](authorization.md).
 
-You may use the [[yii\web\AccessControl]] filter and/or the Role-Based Access Control (RBAC) component
-to implementation authorization.
+You may use the Role-Based Access Control (RBAC) component to implementation authorization.
 
 To simplify the authorization check, you may also override the [[yii\rest\Controller::checkAccess()]] method
 and then call this method in places where authorization is needed. By default, the built-in actions provided
diff --git a/framework/base/Application.php b/framework/base/Application.php
index 33efe2c657..f44edef68e 100644
--- a/framework/base/Application.php
+++ b/framework/base/Application.php
@@ -124,6 +124,10 @@ abstract class Application extends Module
      *     'name' => 'extension name',
      *     'version' => 'version number',
      *     'bootstrap' => 'BootstrapClassName',
+     *     'alias' => [
+     *         '@alias1' => 'to/path1',
+     *         '@alias2' => 'to/path2',
+     *     ],
      * ]
      * ~~~
      */
diff --git a/framework/db/ActiveRecord.php b/framework/db/ActiveRecord.php
index 74b22f89be..ad895e6599 100644
--- a/framework/db/ActiveRecord.php
+++ b/framework/db/ActiveRecord.php
@@ -8,6 +8,7 @@
 
 namespace yii\db;
 
+use Yii;
 use yii\base\InvalidConfigException;
 use yii\helpers\Inflector;
 use yii\helpers\StringHelper;
@@ -376,6 +377,7 @@ class ActiveRecord extends BaseActiveRecord
     public function insert($runValidation = true, $attributes = null)
     {
         if ($runValidation && !$this->validate($attributes)) {
+            Yii::info('Model not inserted due to validation error.', __METHOD__);
             return false;
         }
         $db = static::getDb();
@@ -493,6 +495,7 @@ class ActiveRecord extends BaseActiveRecord
     public function update($runValidation = true, $attributes = null)
     {
         if ($runValidation && !$this->validate($attributes)) {
+            Yii::info('Model not updated due to validation error.', __METHOD__);
             return false;
         }
         $db = static::getDb();
diff --git a/framework/validators/ImageValidator.php b/framework/validators/ImageValidator.php
index ebae6f1762..73ac14ff8e 100644
--- a/framework/validators/ImageValidator.php
+++ b/framework/validators/ImageValidator.php
@@ -132,7 +132,7 @@ class ImageValidator extends FileValidator
             $this->overHeight = Yii::t('yii', 'The image "{file}" is too large. The height cannot be larger than {limit, number} {limit, plural, one{pixel} other{pixels}}.');
         }
         if ($this->wrongMimeType === null) {
-            $this->wrongMimeType = Yii::t('yii', 'Only files with these mimeTypes are allowed: {mimeTypes}.');
+            $this->wrongMimeType = Yii::t('yii', 'Only files with these MIME types are allowed: {mimeTypes}.');
         }
         if (!is_array($this->mimeTypes)) {
             $this->mimeTypes = preg_split('/[\s,]+/', strtolower($this->mimeTypes), -1, PREG_SPLIT_NO_EMPTY);