iOS 7 has bug in handling attachments on S/MIME Encrypted Mail
Since upgrading to iOS 7, my colleagues and I can open attachments on unencrypted e-mail messages just fine. When reading an encrypted message, we can see the message body text but the attachment pulsates inexplicably. I've included a screen-shot (moving GIF) and a brief writeup here...
http://snnyc.com/2013/09/ios7-smime-fail/
Robert Parks
iPhone 4, iOS 6.1.2