Simple Machines Forum (SMF) 1.1.4 allows remote attackers to read a message in private forums by using the advanced search module with the "show results as messages" option, then searching for possible keywords contained in that message.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2007-5913
http://www.securityfocus.com/bid/26508
http://www.securityfocus.com/archive/1/483437/100/0/threaded