blueimp/jQuery-File-Upload — pull request #2769 by francoisjacques (2013-11-26 17:32:10+00:00)
Title: Default the file type to octetstream when unspecified

In the case where the host browser cannot deduce the file type, the default value of the content-type should be application/octet-stream, otherwise the request may end up with an invalid Content-Type header.