MyBB before 1.8.22 allows an open redirect on login.

In MyBB before 1.8.21, an attacker can abuse a default behavior of MySQL on many systems (that leads to truncation of strings that are too long for a database column) to create a PHP shell in the cache directory of a targeted forum via a crafted XML import, as demonstrated by truncation of aaaaaaaaaaaaaaaaaaaaaaaaaa.php.css to aaaaaaaaaaaaaaaaaaaaaaaaaa.php with a 30-character limit, aka theme import stylesheet name RCE.

In MyBB before 1.8.21, an attacker can exploit a parsing flaw in the Private Message / Post renderer that leads to [video] BBCode persistent XSS to take over any forum account, aka a nested video MyCode issue.

MyBB 1.8.14 is not checking for a valid CSRF token, leading to arbitrary deletion of user accounts.

MyBB 1.8.14 has XSS via the Title or Description field on the Edit Forum screen.

A reflected XSS vulnerability in index.php in MyBB 1.8.x through 1.8.19 allows remote attackers to inject JavaScript via the 'upsetting[bburl]' parameter.

A reflected XSS vulnerability in the ModCP Profile Editor in MyBB before 1.8.20 allows remote attackers to inject JavaScript via the 'username' parameter.

A Persistent XSS issue was discovered in the Visual Editor in MyBB before 1.8.19 via a Video MyCode.

An issue was discovered in inc/class_feedgeneration.php in MyBB 1.8.17. On the forum RSS Syndication page, one can generate a URL such as http://localhost/syndication.php?fid=&type=atom1.0&limit=15. The thread titles (within title elements of the generated XML documents) aren't sanitized, leading to XSS.

In the Ban List plugin 1.0 for MyBB, any forum user with mod privileges can ban users and input an XSS payload into the ban reason, which is executed on the bans.php page.

Trash Bin plugin 1.1.3 for MyBB has cross-site scripting (XSS) via a thread subject and a cross-site request forgery (CSRF) via a post subject.

The New Threads plugin before 1.2 for MyBB has XSS.

MyBB 1.8.15, when accessed with Microsoft Edge, mishandles 'target="_blank" rel="noopener"' in A elements, which makes it easier for remote attackers to conduct redirection attacks.

MyBB Group MyBB contains a Incorrect Access Control vulnerability in Private forums that can result in Users can view posts from private forums without having the password. This attack appear to be exploitable via Subscribe to a forum through IDOR. This vulnerability appears to have been fixed in 1.8.15.

MyBB Group MyBB contains a File Inclusion vulnerability in Admin panel (Tools and Maintenance -> Task Manager -> Add New Task) that can result in Allows Local File Inclusion on modern PHP versions and Remote File Inclusion on ancient PHP versions. This attack appear to be exploitable via Must have access to admin panel. This vulnerability appears to have been fixed in 1.8.15.

Multiple cross-site scripting (XSS) vulnerabilities in the MyBB (aka MyBulletinBoard) before 1.8.4 allow remote authenticated users to inject arbitrary web script or HTML via the title parameter in the (1) edit or (2) add action in the user-users module or the (3) finduser action or the name parameter in an (4) edit action in the user-user module or the (5) editprofile action to modcp.php.

Cross-site scripting (XSS) vulnerability in MyBB before 1.6.13 allows remote authenticated users to inject arbitrary web script or HTML via the name parameter in the edit action of the config-profile_fields module.