thoughtbot/paperclip — pull request #1602 by norman (2014-07-16 16:18:38+00:00)
Title: Describe workaround for false spoofing errors

As described in issue #1470, Paperclip can sometimes raise undesired spoofing errors when working with custom extensions. This adds an example workaround in the README using the public API of the mime-types library that will resolve this issue in a way compatible with Paperclip.