CVE-2020-19048 in MyBB
Summary
by MITRE • 08/31/2021
Cross Site Scripting (XSS) in MyBB v1.8.20 allows remote attackers to inject arbitrary web script or HTML via the "Title" field found in the "Add New Forum" page by doing an authenticated POST HTTP request to '/Upload/admin/index.php?module=forum-management&action=add'.
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Analysis
by VulDB Data Team • 09/03/2021
This cross site scripting vulnerability exists in MyBB version 1.8.20 within the administrative forum management interface. The flaw occurs when an authenticated user submits a malicious payload through the title field during forum creation, specifically targeting the admin panel endpoint at /Upload/admin/index.php?module=forum-management&action=add. The vulnerability represents a classic stored XSS attack vector where malicious input is persisted in the application's database and subsequently executed in the context of other users' browsers. This type of vulnerability falls under CWE-79 which categorizes improper neutralization of input during web page generation, specifically addressing the failure to sanitize user-controllable data before incorporating it into dynamically generated web content. The attack requires an authenticated session, meaning that an attacker must first compromise a valid user account with administrative privileges to exploit this vulnerability effectively.
The operational impact of this vulnerability is significant as it enables attackers to execute arbitrary JavaScript code in the browsers of other administrators or users who view the affected forum listings. This could lead to session hijacking, credential theft, or redirection to malicious sites. The vulnerability affects the administrative interface specifically, making it particularly dangerous as it could allow an attacker to escalate privileges or gain deeper access to the forum's backend. According to ATT&CK framework, this maps to technique T1566.001 which covers credential harvesting through phishing attacks, and T1059.007 which involves the execution of scripts through web applications. The vulnerability demonstrates a failure in input validation and output encoding practices within the MyBB administrative components.
Mitigation strategies should focus on implementing proper input sanitization and output encoding mechanisms throughout the application's codebase. The recommended approach involves validating all user inputs against a strict whitelist of acceptable characters and encoding all output data before rendering it in web pages. Administrators should immediately upgrade to MyBB version 1.8.21 or later where this vulnerability has been patched. Additionally, implementing Content Security Policy headers can provide an additional layer of protection against XSS attacks by restricting the sources from which scripts can be loaded. Regular security audits and input validation testing should be conducted to identify similar vulnerabilities in other parts of the application. The vulnerability highlights the importance of principle of least privilege in administrative interfaces and demonstrates how authenticated vulnerabilities can be leveraged for more severe security breaches. Organizations should also implement regular security training for administrators to recognize potential social engineering attempts that could lead to account compromise and subsequent exploitation of such vulnerabilities.