In MyBB before version 1.8.24, the custom MyCode (BBCode) for the visual editor doesn't escape input properly when rendering HTML, resulting in a DOM-based XSS vulnerability. The weakness can be exploited by pointing a victim to a page where the visual editor is active (e.g. as a post or Private Message) and operates on a maliciously crafted MyCode message. This may occur on pages where message content is pre-filled using a GET/POST parameter, or on reply pages where a previously saved malicious message is quoted. After upgrading MyBB to 1.8.24, make sure to update the version attribute in the `codebuttons` template for non-default themes to serve the latest version of the patched `jscripts/bbcodes_sceditor.js` file.

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.

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.

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.

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.

The installer in MyBB before 1.8.13 has XSS.

The installer in MyBB before 1.8.13 allows remote attackers to execute arbitrary code by writing to the configuration file.

In MyBB before 1.8.11, the smilie module allows Directory Traversal via the pathfolder parameter.

In MyBB before 1.8.11, the Email MyCode component allows XSS, as demonstrated by an onmouseover event.

MyBB before 1.8.11 allows remote attackers to bypass an SSRF protection mechanism.

Cross-site scripting (XSS) vulnerability in the Users module in the Admin control panel in MyBB (aka MyBulletinBoard) before 1.8.8 and MyBB Merge System before 1.8.8 might allow remote attackers to inject arbitrary web script or HTML via unspecified vectors.

MyBB (aka MyBulletinBoard) before 1.8.8 and MyBB Merge System before 1.8.8 allow remote attackers to have unspecified impact via vectors related to "loose comparison false positives."

Cross-site scripting (XSS) vulnerability in the Admin control panel in MyBB (aka MyBulletinBoard) before 1.8.8 and MyBB Merge System before 1.8.8 allows remote attackers to inject arbitrary web script or HTML via unspecified vectors.

MyBB (aka MyBulletinBoard) before 1.8.8 on Windows and MyBB Merge System before 1.8.8 on Windows might allow remote attackers to obtain sensitive information from ACP backups via vectors involving a short name.

The fetch_remote_file function in MyBB (aka MyBulletinBoard) before 1.8.8 and MyBB Merge System before 1.8.8 allows remote attackers to conduct server-side request forgery (SSRF) attacks via unspecified vectors.