Take the basename of the upload’s original filename. This handles the full Windows paths given by Internet Explorer (and perhaps other broken user agents) without affecting those which give the lone filename. The Windows regexp is adapted from Perl’s File::Basename.
# File actionpack/lib/action_dispatch/http/upload.rb, line 18 def original_filename unless defined? @original_filename @original_filename = unless original_path.blank? if original_path =~ /^(?:.*[:\\\/])?(.*)/m $1 else File.basename original_path end end end @original_filename end