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.

MyBB (aka MyBulletinBoard) 1.4.2 does not properly handle an uploaded file with a nonstandard file type that contains HTML sequences, which allows remote attackers to cause that file to be processed as HTML by Internet Explorer's content inspection, aka "Incomplete protection against MIME-sniffing." NOTE: this could be leveraged for XSS and other attacks.

MyBB (aka MyBulletinBoard) 1.4.2 uses insufficient randomness to compose filenames of uploaded files used as attachments, which makes it easier for remote attackers to read these files by guessing filenames.

Cross-site scripting (XSS) vulnerability in the redirect function in functions.php in MyBB (aka MyBulletinBoard) 1.4.2 allows remote attackers to inject arbitrary web script or HTML via the url parameter in a removesubscriptions action to moderation.php, related to use of the ajax option to request a JavaScript redirect. NOTE: this can be leveraged to execute PHP code and bypass cross-site request forgery (CSRF) protection.