I'd like to receive an attachment file. What should I do?
Yes, You MUST set some up as below:
(1) The Ylt;form Tag was changed by this update, so, please re-copy the tag on your settings window, it is (2) area, red area. You must replace the <form Tag at your html for receiving an attachment file.
(2) If you haven't ever uploaded via "Media" in your admin window, please upload some file via "Media" window. If you do so, a new directory "uploads" will be created in /wp-content/.
(3) Set <input id="" name="attachment_file" class="" type="file"/> to your html form.