Webform_node results_export download

I had unpublished this not realizing it is the public post of an originally private issue. I've added a note about that to the issue summary.

Adding the appropriate tag.

I think the below code should do the trick.

      // Sanitize $file_name to remove directory traversing.
      $file_name = str_replace(['..', '/', '\\'], '', $query['filename']);
      $file_path = $this->submissionExporter->getFileTempDirectory() . '/' . $file_name;

Tested, and this fix works for me (in a clean setup).

Please make a merge request.