Hastymail 1.0.1 and earlier (stable) and 1.1 and earlier (development) does not send the "attachment" parameter in the Content-Disposition field for attachments, which causes the attachment to be rendered inline by Internet Explorer when the victim clicks the download link, which facilitates cross-site scripting (XSS) and possibly other attacks.
https://exchange.xforce.ibmcloud.com/vulnerabilities/17091
http://www.securityfocus.com/bid/11022
http://securitytracker.com/id?1011054
http://secunia.com/advisories/12358
http://hastymail.sourceforge.net/security.php
http://archives.neohapsis.com/archives/bugtraq/2004-08/0322.html