CVE-2016-9405 in MyBB
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in member validation 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 unspecified vectors.
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Analysis
by VulDB Data Team • 08/08/2020
The vulnerability identified as CVE-2016-9405 represents a critical cross-site scripting flaw within the member validation functionality of MyBB, a widely used open-source bulletin board system. This vulnerability affects versions prior to 1.8.7 of both MyBB and its associated Merge System, creating a significant security risk for administrators and users who rely on these platforms for community management and discussion forums. The flaw resides in the validation mechanisms that process user inputs during membership registration and account verification processes, where insufficient sanitization allows malicious actors to inject malicious scripts that can execute in the context of other users' browsers.
The technical nature of this vulnerability stems from improper input validation and output encoding within the member validation workflow. When users attempt to register or validate their accounts, the system fails to adequately sanitize user-supplied data before processing it through the validation routines. This weakness creates an environment where attackers can craft malicious inputs containing script code that gets executed when other users view the affected pages or interact with the validated member data. The unspecified vectors suggest that multiple input points within the validation process could be exploited, making the attack surface broader than initially apparent. This type of vulnerability typically maps to CWE-79 - Improper Neutralization of Input During Web Page Generation, which is a fundamental weakness in web application security design.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, and data exfiltration. When executed successfully, the XSS payload can steal cookies, modify user interface elements, redirect users to malicious sites, or even execute commands on behalf of the victim. In a forum environment, this could lead to the compromise of user accounts, manipulation of forum content, and potential escalation to administrative privileges if attackers can exploit additional vulnerabilities. The vulnerability particularly affects user trust and platform integrity, as compromised users may unknowingly become vectors for further attacks within the community. According to ATT&CK framework, this vulnerability aligns with T1059.007 - Command and Scripting Interpreter: JavaScript, and T1531 - Account Access Removal, as it enables unauthorized access to user sessions and potentially administrative controls.
Mitigation strategies for CVE-2016-9405 primarily focus on immediate patching and implementation of robust input validation measures. Organizations should prioritize upgrading to MyBB version 1.8.7 or later, which contains the necessary fixes for this vulnerability. Additionally, implementing comprehensive input sanitization at multiple points in the application, including the member validation process, can provide defense-in-depth protection. Web Application Firewalls should be configured to detect and block suspicious script patterns in user inputs, while output encoding should be enforced for all dynamic content rendered in web pages. Security headers such as Content Security Policy should be implemented to restrict script execution and prevent unauthorized code injection. Regular security audits and penetration testing should be conducted to identify similar vulnerabilities in other components of the forum infrastructure, and user education regarding suspicious links and scripts should be emphasized to reduce successful exploitation attempts.