If you include a custom field with type = FILE in a Profile, and embed that Profile in an Online Contribution page OR an Event Registration page - the field shows up in the initial form, and can be populated by the user. However, we don't persist the data for the uploaded file (not sure we actually upload it either), and on the Confirm page - we show the Browse/Input form field element again (instead of displaying the uploaded file name).
We should fix the code to handle this case - which will mean some additional logic to pass the uploaded file handle to Confirm / postProcess().
— Original Post ----
An event registration form has a file field to pick a file.
When a user tries to register, he is given the chance to select a file.
When he presses the continue button and is taken to the confirmation screen, the file has disappeared.
If he selects it there, it also happily accepts it and then does nothing.