Monkey-patch StrongParameters for ::UploadedFile

config/initializers/workhorse_multipart.rb

 Rails.application.configure do |config|
   config.middleware.use(Gitlab::Middleware::Multipart)
 end
+
+module Gitlab
+  module StrongParameterScalars
+    GITLAB_PERMITTED_SCALAR_TYPES = [::UploadedFile]
+
+    def permitted_scalar?(value)
+      super || GITLAB_PERMITTED_SCALAR_TYPES.any? { |type| value.is_a?(type) }
+    end
+  end
+end
+
+module ActionController
+  class Parameters
+    prepend Gitlab::StrongParameterScalars
+  end
+end