CVE-2016-9404 in MyBB
Summary
by MITRE
Cross-site scripting (XSS) vulnerability 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 related to login.
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Analysis
by VulDB Data Team • 08/08/2020
The vulnerability identified as CVE-2016-9404 represents a critical cross-site scripting flaw affecting MyBB bulletin board software and its associated merge system. This vulnerability exists in versions prior to 1.8.7 and specifically targets the authentication and login mechanisms of the platform. The flaw allows remote attackers to inject malicious web scripts or HTML content into the application's user interface, creating a persistent security risk that can affect all users interacting with the vulnerable system. The vulnerability's classification as CWE-79 indicates a classic XSS weakness where user-controllable input is not properly sanitized before being rendered in web pages, making it a prime target for exploitation by malicious actors seeking to compromise user sessions or deface web properties.
The technical exploitation of this vulnerability occurs through the login process where attacker-controlled input can be processed and reflected back to users without adequate sanitization measures. When users authenticate or interact with login-related components, malicious payloads embedded in the input fields can execute within the context of other users' browsers. This creates a dangerous scenario where an attacker could steal session cookies, redirect users to malicious sites, or inject persistent malware that executes whenever affected users access the vulnerable application. The attack vector specifically leverages the trust relationship between the web application and its users, making it particularly effective as users naturally interact with login forms and authentication pages.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it can enable more sophisticated attacks within the compromised environment. Attackers can exploit the XSS vulnerability to perform session hijacking, steal administrative credentials, or create backdoor access points within the forum infrastructure. The vulnerability affects the entire user base of vulnerable installations, making it a high-priority concern for administrators managing online communities and discussion platforms. Organizations relying on MyBB for their web presence face significant risks including potential data breaches, reputational damage, and the compromise of user privacy. The attack surface is particularly concerning given that login pages are frequently accessed and often contain sensitive user information that could be exploited through session manipulation or credential theft.
Mitigation strategies for CVE-2016-9404 primarily focus on immediate software updates to version 1.8.7 or later, which contain the necessary patches to address the XSS vulnerability. System administrators should conduct comprehensive vulnerability assessments to identify all installations running affected versions and prioritize patch deployment across their infrastructure. Additional protective measures include implementing robust input validation and output encoding mechanisms, deploying web application firewalls to filter malicious payloads, and establishing monitoring procedures to detect potential exploitation attempts. The remediation process should also involve user education regarding safe browsing practices and the importance of recognizing suspicious website behavior. Organizations should consider implementing content security policies to prevent unauthorized script execution and maintain regular security audits to ensure continued protection against similar vulnerabilities. This vulnerability demonstrates the critical importance of maintaining up-to-date software and proper security hygiene in web application environments, as it directly aligns with ATT&CK technique T1213 for credential access and T1059 for command and scripting interpreter usage patterns.