A problem with how WS-Security handled MTOM attachments resulted in attachments being sent as a base64 encoded byte array in the SOAP body, and not as a MIME attachment. Additionally, customers wanting to use MTOM attachments with signing were limited to having the signature generated on the attachment contents. Depending on the attachment size, this resulted in performance implications. The fix prevents WS-Security from incorrectly encoding attachments and gives customers alternative ways of generating signing signatures.