CVE-2016-9407 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 involving Mod control panel logs.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 08/08/2020
The cross-site scripting vulnerability identified as CVE-2016-9407 affects MyBulletinBoard (MyBB) versions prior to 1.8.7 and its associated Merge System. This weakness represents a classic client-side injection flaw that enables remote attackers to execute malicious scripts within the context of other users' browsers. The vulnerability specifically manifests in the Mod control panel logs functionality, where insufficient input validation and output sanitization create opportunities for attackers to inject malicious code. The flaw resides in how the application processes and displays log entries from moderator activities, particularly when these entries contain user-supplied data that is not properly escaped or filtered before rendering in web pages.
The technical implementation of this vulnerability stems from inadequate sanitization of data within the administrative logging system. When moderators perform actions within the control panel, these activities are recorded in log entries that are subsequently displayed to other administrators. Attackers can exploit this by crafting malicious input that includes script tags or other HTML elements within the log data. The vulnerability follows CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') which is a fundamental web application security weakness. The attack vector leverages the trust relationship between the web application and its users, allowing malicious code execution in the victim's browser context through the manipulation of log entries that are displayed in the administrative interface.
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 redirection to malicious sites. An attacker who successfully exploits this vulnerability could gain access to administrative privileges if they can manipulate log entries that are viewed by administrators. The risk is particularly elevated in environments where multiple administrators have access to the control panel and where log entries are frequently reviewed. This vulnerability can be exploited through various attack methods including reflected XSS where the malicious payload is reflected back to the user through the log display mechanism, or stored XSS where the payload is permanently stored in the application's database and executed each time the log entry is rendered.
Mitigation strategies for CVE-2016-9407 primarily involve implementing proper input validation and output encoding techniques. Organizations should ensure that all user-supplied data, particularly data that appears in administrative interfaces, is properly escaped before being displayed. The fix typically involves updating to MyBB version 1.8.7 or later, which includes comprehensive sanitization of log data and improved XSS protection mechanisms. Security practitioners should also implement Content Security Policy (CSP) headers to provide additional protection against script injection attacks. The vulnerability demonstrates the importance of following secure coding practices as outlined in the OWASP Top Ten and aligns with ATT&CK technique T1059.001 - Command and Scripting Interpreter: PowerShell for similar injection vulnerabilities. Organizations should also consider implementing web application firewalls and regular security scanning to detect and prevent exploitation attempts. The remediation process should include comprehensive testing of all administrative interfaces to ensure that no similar vulnerabilities exist in other parts of the application's codebase.