// Delete isXmlHttpRequest

classes/controller/Controller.php

@@ -140,7 +140,7 @@ abstract class ControllerCore
 		$this->context = Context::getContext();
 		$this->context->controller = $this;
 		// Usage of ajax parameter is deprecated
-		$this->ajax = Tools::getValue('ajax') || Tools::isSubmit('ajax') || $this->isXmlHttpRequest();
+		$this->ajax = Tools::getValue('ajax') || Tools::isSubmit('ajax');
 	}
 
 	/**