Horde-IMP is the Internet Messaging Program. It is written in PHP and provides webmail access to IMAP and POP3 accounts.
Horde-IMP fails to properly sanitize email messages that contain malicious HTML or script code so that it is not safe for users of Internet Explorer when using the inline MIME viewer for HTML messages.
By enticing a user to read a specially crafted e-mail, an attacker can execute arbitrary scripts running in the context of the victim's browser. This could lead to a compromise of the user's webmail account, cookie theft, etc.
Do not use Internet Explorer to access Horde-IMP.
All Horde-IMP users should upgrade to the latest stable version:
# emerge sync
# emerge -pv ">=www-apps/horde-imp-3.2.5"
# emerge ">=www-apps/horde-imp-3.2.5"