CVE-2015-8975 in MyBB
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the error handler in MyBB (aka MyBulletinBoard) before 1.6.18 and 1.8.x before 1.8.6 and MyBB Merge System before 1.8.6 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 CVE-2015-8975 vulnerability represents a critical cross-site scripting flaw within the error handling mechanisms of MyBB, a widely used open-source bulletin board system. This vulnerability affects versions prior to 1.6.18 and 1.8.x versions before 1.8.6, as well as the MyBB Merge System before version 1.8.6, creating a significant security risk for numerous web forums and community platforms that rely on this software. The flaw resides specifically in how the application processes and displays error messages, making it a prime target for malicious actors seeking to exploit user sessions and compromise forum integrity.
The technical nature of this vulnerability stems from improper input sanitization within the error handler component of MyBB's codebase. When the system encounters an error condition, it processes and displays error messages to users without adequate validation or encoding of user-supplied data. This allows attackers to inject malicious scripts or HTML content through unspecified vectors that typically involve manipulating input parameters that trigger error conditions. The vulnerability manifests when error messages are rendered in web browsers, providing attackers with an execution environment for their malicious payloads. According to CWE classification, this represents a classic cross-site scripting weakness categorized under CWE-79, which specifically addresses improper neutralization of input during web output, making it particularly dangerous for web applications.
The operational impact of CVE-2015-8975 extends far beyond simple script injection, as it provides attackers with the capability to hijack user sessions, steal sensitive information, and potentially gain administrative privileges within affected forums. Attackers can craft malicious error conditions that, when triggered, execute scripts in the context of authenticated users, enabling session theft through cookie manipulation, redirection to malicious sites, or data exfiltration. The vulnerability's persistence across multiple versions of MyBB indicates a fundamental flaw in the error handling architecture that could affect thousands of active forums worldwide. From an ATT&CK framework perspective, this vulnerability maps to T1566 (Phishing) and T1071.001 (Application Layer Protocol: Web Protocols) as attackers can leverage the XSS to deliver malicious content through forum interfaces. The attack surface is particularly concerning because error conditions are often triggered by legitimate user activities, making the exploitation less detectable and more likely to succeed in real-world scenarios.
Mitigation strategies for this vulnerability require immediate patching of affected MyBB installations to versions 1.6.18 or later for the 1.6.x series, and 1.8.6 or later for the 1.8.x series, along with updating the MyBB Merge System to version 1.8.6 or higher. Organizations should implement comprehensive input validation and output encoding mechanisms throughout their web applications, particularly in error handling components, following secure coding practices that align with OWASP recommendations. Additionally, deployment of web application firewalls and content security policies can provide additional layers of protection against exploitation attempts. Regular security audits and penetration testing of forum systems are essential to identify similar vulnerabilities in other components of the application stack. The vulnerability serves as a reminder of the critical importance of secure error handling practices and the potential consequences of inadequate input validation in web applications.