Fixes #3458: Fixed the bug that the image rendered by `CaptchaAction` was using…

framework/CHANGELOG.md

@@ -27,6 +27,7 @@ Yii Framework 2 Change Log
 - Bug #3368: Fix for comparing numeric attributes in JavaScript (technixp)
 - Bug #3431: Allow using extended ErrorHandler class from the app namespace (cebe)
 - Bug #3436: Fixed the issue that `ServiceLocator` still returns the old component after calling `set()` with a new definition (qiangxue)
+- Bug #3458: Fixed the bug that the image rendered by `CaptchaAction` was using a wrong content type (MDMunir, qiangxue)
 - Bug: Fixed inconsistent return of `\yii\console\Application::runAction()` (samdark)
 - Enh #2264: `CookieCollection::has()` will return false for expired or removed cookies (qiangxue)
 - Enh #2435: `yii\db\IntegrityException` is now thrown on database integrity errors instead of general `yii\db\Exception` (samdark)

framework/captcha/CaptchaAction.php

@@ -11,6 +11,7 @@ use Yii;
 use yii\base\Action;
 use yii\base\InvalidConfigException;
 use yii\helpers\Url;
+use yii\web\Response;
 
 /**
  * CaptchaAction renders a CAPTCHA image.
@@ -127,7 +128,7 @@ class CaptchaAction extends Action
             ]);
         } else {
             $this->setHttpHeaders();
-
+            Yii::$app->response->format = Response::FORMAT_RAW;
             return $this->renderImage($this->getVerifyCode());
         }
     }