create an initializer to override Paperclip's classes file_command_content_type_detector.rb and media_type_spoof_detector.rb

file_command_content_type_detector.rb

module Paperclip
  class FileCommandContentTypeDetector
    SENSIBLE_DEFAULT = "application/octet-stream"

    def initialize(filename)
      @filename = filename
    end

    def detect
      type_from_file_command
    end

    private

    def type_from_file_command
      type = begin
        # On BSDs, `file` doesn't give a result code of 1 if the file doesn't exist.
        Paperclip.log("Check mime_type of #{@filename}")
        MIME::Types.type_for(@filename).first.nil? ? nil : MIME::Types.type_for(@filename).first.content_type 

      rescue nil
      end

      if type.nil? || type.match(/\(.*?\)/)
        type = SENSIBLE_DEFAULT
      end
      type.split(/[:;\s]+/)[0]
    end

  end
end