Is it possible to restrict file types that can be uploaded through a fileUpload

Using validations, we can restrict the file types. See below post, we can validate the file type without submitting the form.
forum.appian.com/.../e-153370

@scottl Are you asking this question in the context of SAIL? If so, a hack was found by @adela which has been described at https://forum.appian.com/suite/tempo/entry/e-153370 and please do remember that it is not officially approved by Appian. Keeping the hack aside, I guess the only way to do it is to make a check after the submission of the form as per my knowledge.

Thanks all.