Horde MIME Viewer versions 3.0.7 and below suffer from a flaw where gziped content is not sanitized before displaying it. This can allow for cross site scripting attacks.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/41921/hordeMIMEXSS.txt
Source: https://packetstormsecurity.com/files/41921/hordeMIMEXSS.txt.html