core-bundle/src/Resources/contao/controllers/BackendCustom.php
public function run()
	{
		try {
			$version = PackageUtil::getVersion('contao/core-bundle');
		} catch (\OutOfBoundsException $e) {
			$version = PackageUtil::getVersion('contao/contao');
		}

		$this->Template->version = $GLOBALS['TL_LANG']['MSC']['version'] . ' ' . $version;

		// Ajax request
		if ($_POST && Environment::get('isAjaxRequest'))
		{
			$this->objAjax = new Ajax(Input::post('action'));
			$this->objAjax->executePreActions();
		}

		return $this->output();
	}
public function run()
	{
		try {
			$version = PackageUtil::getVersion('contao/core-bundle');
		} catch (\OutOfBoundsException $e) {
			$version = PackageUtil::getVersion('contao/contao');
		}

		$this->Template->version = $GLOBALS['TL_LANG']['MSC']['version'] . ' ' . $version;

		// Ajax request
		if ($_POST && Environment::get('isAjaxRequest'))
		{
			$this->objAjax = new Ajax(Input::post('action'));
			$this->objAjax->executePreActions();
		}

		return $this->output();
	}
Run the controller and parse the template

@return Response