The password reset functionality in Simple Machines Forum (SMF) 1.0.x before 1.0.14, 1.1.x before 1.1.6, and 2.0 before 2.0 beta 4 includes clues about the random number generator state within a hidden form field and generates predictable validation codes, which allows remote attackers to modify passwords of other users and gain privileges.
https://www.exploit-db.com/exploits/6392
https://exchange.xforce.ibmcloud.com/vulnerabilities/44931
http://www.simplemachines.org/community/index.php?topic=260145.0