MHonArc 2.5.2 and earlier does not properly filter Javascript from archived e-mail messages, which could allow remote attackers to execute script in web clients by (1) splitting the SCRIPT tag into smaller pieces, (2) including the script in a SRC argument to an IMG tag, or (3) using "&={script}" syntax.
http://www.securityfocus.com/bid/4546
http://www.mhonarc.org/MHonArc/CHANGES
http://www.iss.net/security_center/static/8894.php
http://www.debian.org/security/2002/dsa-163
http://archives.neohapsis.com/archives/bugtraq/2002-04/0260.html