CVE-2016-9408 in MyBB
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Mod control panel in MyBB (aka MyBulletinBoard) before 1.8.7 and MyBB Merge System before 1.8.7 might allow remote attackers to inject arbitrary web script or HTML via vectors involving editing users.
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Analysis
by VulDB Data Team • 08/08/2020
The CVE-2016-9408 vulnerability represents a critical cross-site scripting flaw discovered in MyBB, a popular bulletin board system widely used for online forums. This vulnerability specifically affects the Mod control panel functionality within MyBB versions prior to 1.8.7 and the MyBB Merge System versions before 1.8.7, creating a significant security risk for administrators and users who interact with the moderation features of these platforms. The flaw resides in how the system handles user input during the editing process, particularly when administrators modify user accounts through the moderation interface. This vulnerability is classified under CWE-79 as a classic cross-site scripting vulnerability, which occurs when user-supplied data is not properly sanitized before being rendered back to users in the web interface.
The technical exploitation of this vulnerability occurs when a remote attacker can manipulate the user editing functionality within the moderation control panel to inject malicious scripts or HTML code. When administrators or other users view the modified user profiles, the injected code executes in their browsers, potentially leading to session hijacking, credential theft, or other malicious activities. The attack vector specifically involves the editing of user accounts through the Mod control panel, where input validation is insufficient to prevent malicious payloads from being stored and subsequently executed. This type of vulnerability falls under the ATT&CK technique T1566.001 for "Phishing with Social Engineering" and T1059.001 for "Command and Scripting Interpreter" as it enables attackers to execute arbitrary code within victim browsers.
The operational impact of CVE-2016-9408 extends beyond simple script injection, as it provides attackers with potential access to administrative privileges and sensitive forum data. An attacker who successfully exploits this vulnerability could manipulate user accounts, modify forum content, access private messages, or even escalate privileges to gain full administrative control of the bulletin board system. The vulnerability is particularly dangerous because it affects the moderation interface, which is typically accessed by trusted administrators who may have elevated privileges within the system. Organizations using MyBB versions prior to 1.8.7 face significant risk of data compromise, user privacy violations, and potential service disruption. The vulnerability also creates opportunities for attackers to establish persistent access through malicious scripts that can monitor user activities or redirect them to phishing sites.
Mitigation strategies for CVE-2016-9408 should prioritize immediate patching of MyBB installations to version 1.8.7 or later, which includes proper input sanitization and validation mechanisms. System administrators should implement additional security measures such as content security policy headers to limit script execution, regular monitoring of user account modifications, and comprehensive input validation for all user-supplied data. Network administrators should consider implementing web application firewalls to detect and block malicious script injection attempts. Organizations should also conduct regular security assessments of their MyBB installations, review user access controls, and maintain up-to-date backups to ensure rapid recovery in case of successful exploitation. The vulnerability highlights the importance of proper input validation and output encoding in web applications, particularly in administrative interfaces where privileged users interact with potentially untrusted data.