The my_rand function in functions.php in MyBB (aka MyBulletinBoard) before 1.4.12 does not properly use the PHP mt_rand function, which makes it easier for remote attackers to obtain access to an arbitrary account by requesting a reset of the account's password, and then conducting a brute-force attack.

Cross-site request forgery (CSRF) vulnerability in usercp2.php in MyBB (aka MyBulletinBoard) before 1.4.12 allows remote attackers to hijack the authentication of unspecified victims via unknown vectors.

MyBB (aka MyBulletinBoard) before 1.4.12 does not properly handle a configuration with a visible forum that contains hidden threads, which allows remote attackers to obtain sensitive information by reading the Latest Threads block of the Portal Page.

MyBB (aka MyBulletinBoard) before 1.4.12 does not properly restrict uid values for group join requests, which allows remote attackers to cause a denial of service (resource consumption) by using guest access to submit join request forms for moderated groups, related to usercp.php and managegroup.php.

MyBB (aka MyBulletinBoard) before 1.4.12 allows remote authenticated users to bypass intended restrictions on the number of [img] MyCodes by editing a post after it has been created.

member.php in MyBB (aka MyBulletinBoard) before 1.4.12 makes a certain superfluous call to the SQL COUNT function, which allows remote attackers to cause a denial of service (resource consumption) by making requests to member.php that trigger scans of the entire users table.