Implement CSRF token by default

Implement CSRF protection on CMS for postback handling

config/cms.php

@@ -332,7 +332,7 @@ return [
     |
     */
 
-    'enableCsrfProtection' => false,
+    'enableCsrfProtection' => true,
 
     /*
     |--------------------------------------------------------------------------

modules/cms/classes/Controller.php

@@ -337,6 +337,7 @@ class Controller
         if (
             $useAjax &&
             ($handler = post('_handler')) &&
+            ($this->verifyCsrfToken()) &&
             ($handlerResponse = $this->runAjaxHandler($handler)) &&
             $handlerResponse !== true
         ) {
@@ -1355,4 +1356,32 @@ class Controller
             }
         }
     }
+
+    //
+    // Security
+    //
+
+    /**
+     * Checks the request data / headers for a valid CSRF token.
+     * Returns false if a valid token is not found. Override this
+     * method to disable the check.
+     * @return bool
+     */
+    protected function verifyCsrfToken()
+    {
+        if (!Config::get('cms.enableCsrfProtection')) {
+            return true;
+        }
+
+        if (in_array(Request::method(), ['HEAD', 'GET', 'OPTIONS'])) {
+            return true;
+        }
+
+        $token = Request::input('_token') ?: Request::header('X-CSRF-TOKEN');
+
+        return hash_equals(
+            Session::token(),
+            $token
+        );
+    }
 }