MyBB Last User's Threads in Profile Plugin 1.2 contains a persistent cross-site scripting vulnerability that allows attackers to inject malicious scripts by crafting thread subjects with script tags. Attackers can create threads with script payloads in the subject field that execute when users visit the attacker's profile page.
MyBB My Arcade Plugin 1.3 contains a persistent cross-site scripting vulnerability that allows authenticated users to inject malicious scripts through arcade game score comments. Attackers can add crafted HTML and JavaScript payloads in the comment field that execute when other users view or edit the comment.
MyBB Downloads Plugin 2.0.3 contains a persistent cross-site scripting vulnerability that allows regular members to inject malicious scripts through the download title field. Attackers can submit a new download with HTML/JavaScript code in the title parameter, which executes when administrators validate the download in downloads.php.
MyBB Like Plugin 3.0.0 contains a stored cross-site scripting vulnerability. Authenticated attackers can inject script payloads into post or thread subjects; when other users view a profile that displays the attacker's liked posts, the unsanitized subject is rendered, executing the script in the viewer's browser.
MyBB Delete Account Plugin 1.4 contains a cross-site scripting vulnerability in the account deletion reason input field. Attackers can inject malicious scripts that will execute in the admin interface when viewing delete account reasons.
MyBB Trending Widget Plugin 1.2 contains a cross-site scripting vulnerability that allows attackers to inject malicious scripts through thread titles. Attackers can modify thread titles with script payloads that will execute when other users view the trending widget.
MyBB Thread Redirect Plugin 0.2.1 contains a cross-site scripting vulnerability in the custom text input field for thread redirects. Attackers can inject malicious SVG scripts that will execute when other users view the thread, allowing arbitrary script execution.
MyBB 1.8.32 contains a chained vulnerability that allows authenticated administrators to bypass avatar upload restrictions and execute arbitrary code. Attackers can modify upload path settings, upload a malicious PHP-embedded image file, and execute commands through the language configuration editing interface.
myBB Forums 1.8.26 contains a stored cross-site scripting vulnerability in the forum announcement system that allows authenticated administrators to inject malicious scripts when creating announcements. Attackers can exploit this vulnerability by inserting script payloads in the announcement title field when adding announcements through the 'Forums and Posts' > 'Forum Announcements' interface, causing arbitrary JavaScript to execute when the announcement is displayed on the forum.
myBB Forums 1.8.26 contains a stored cross-site scripting vulnerability in the forum management system that allows authenticated administrators to inject malicious scripts when creating new forums. Attackers can exploit this vulnerability by inserting script payloads in the forum title field when adding new forums through the 'Forums and Posts' > 'Forum Management' interface, causing arbitrary JavaScript to execute when the forum listing is viewed.
myBB Forums 1.8.26 contains a stored cross-site scripting vulnerability in the template management system that allows authenticated administrators to inject malicious scripts when creating new templates. Attackers can exploit this vulnerability by inserting script payloads in the template title field when adding new templates through the 'Templates and Style' > 'Templates' > 'Manage Templates' > 'Global Templates' interface, causing arbitrary JavaScript to execute when the template is viewed.
myBB version 1.6.4 was distributed with an unauthorized backdoor embedded in the source code. The backdoor allowed remote attackers to execute arbitrary PHP code by injecting payloads into a specially crafted collapsed cookie. This vulnerability was introduced during packaging and was not part of the intended application logic. Exploitation requires no authentication and results in full compromise of the web server under the context of the web application.
MyBB is free and open source forum software. Prior to version 1.8.39, the search component does not validate permissions correctly, which allows attackers to determine the existence of hidden (draft, unapproved, or soft-deleted) threads containing specified text in the title. The visibility state (`mybb_threads.visible` integer column) of threads is not validated in internal search queries, whose result is used to output a general success or failure of the search. While MyBB validates permissions when displaying the final search results, a search operation that internally produces at least one result outputs a redirect response (as a HTTP redirect, or a success message page with delayed redirect, depending on configuration). On the other hand, a search operation that internally produces no results outputs a corresponding message in the response without a redirect. This allows a user to determine whether threads matching title search parameters exist, including draft threads (`visible` with a value of `-2`), soft-deleted threads (`visible` with a value of `-1`), and unapproved threads (`visible` with a value of `0`); in addition to displaying generally visible threads (`visible` with a value of `1`). This vulnerability does not affect other layers of permissions. In order to exploit the vulnerability, the user must have access to the search functionality, and general access to forums containing the thread(s). The vulnerability does not expose the message content of posts. MyBB 1.8.39 resolves this issue.
MyBB is free and open source forum software. Prior to version 1.8.39, the upgrade component does not validate user input properly, which allows attackers to perform local file inclusion (LFI) via a specially crafted parameter value. In order to exploit the vulnerability, the installer must be unlocked (no `install/lock` file present) and the upgrade script must be accessible (by re-installing the forum via access to `install/index.php`; when the forum has not yet been installed; or the attacker is authenticated as a forum administrator). MyBB 1.8.39 resolves this issue.
An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the Add Mycode function. NOTE: the Supplier disputes this because of the allowed actions of Board administrators and because of SSRF mitigation.
An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the Mail function. NOTE: the Supplier disputes this because of the allowed actions of Board administrators and because of SSRF mitigation.
An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the Change Avatar function. NOTE: the Supplier disputes this because of the allowed actions of Board administrators and because of SSRF mitigation.
An issue in MyBB 1.8.38 allows a remote attacker to obtain sensitive information via the Import a Theme function. NOTE: the Supplier disputes this because of the allowed actions of Board administrators and because of SSRF mitigation.
A stored cross-site scripting (XSS) vulnerability in the component install\index.php of MyBB v1.8.38 allows attackers to execute arbitrary web scripts or HTML via a crafted payload injected into the Website Name parameter. NOTE: this is disputed by the Supplier because Website Name can only be set by an administrator, who may use JavaScript if they wish.
MyBB is a free and open source forum software. The default list of disallowed remote hosts does not contain the `127.0.0.0/8` block, which may result in a Server-Side Request Forgery (SSRF) vulnerability. The Configuration File's _Disallowed Remote Addresses_ list (`$config['disallowed_remote_addresses']`) contains the address `127.0.0.1`, but does not include the complete block `127.0.0.0/8`. MyBB 1.8.38 resolves this issue in default installations. Administrators of installed boards should update the existing configuration (`inc/config.php`) to include all addresses blocked by default. Additionally, users are advised to verify that it includes any other IPv4 addresses resolving to the server and other internal resources. Users unable to upgrade may manually add 127.0.0.0/8' to their disallowed address list.