source: https://www.securityfocus.com/bid/6591/info

It has been reported that a problem exists in the Reminder.php script distributed as part of YaBB SE. Due to insufficient sanitizing of input, it is possible for a remote user to inject arbitrary SQL into the database used by YaBB SE that could be used to reset or change the password of a user. 

http://www.example.com/yabbse/Reminder.php?searchtype=esearch&user=[yourusername]'%20or%20memberName='[otherusername]