glFusion before 1.1.3 performs authentication with a user-provided password hash instead of a password, which allows remote attackers to gain privileges by obtaining the hash and using it in the glf_password cookie, aka "User Masquerading." NOTE: this can be leveraged with a separate SQL injection vulnerability to steal hashes.
https://www.exploit-db.com/exploits/8347
http://www.glfusion.org/wiki/doku.php?id=glfusion:whatsnew