CVE-2019-11871 in Custom Field Suite Plugin
Summary
by MITRE
The Custom Field Suite plugin before 2.5.15 for WordPress has XSS for editors or admins.
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Analysis
by VulDB Data Team • 09/15/2023
The vulnerability identified as CVE-2019-11871 affects the Custom Field Suite plugin for WordPress, specifically versions prior to 2.5.15, creating a cross-site scripting weakness that can be exploited by users with editor or administrator privileges. This security flaw resides within the plugin's handling of user input in custom field configurations, where insufficient output sanitization allows malicious scripts to be injected and subsequently executed in the context of other users' browsers. The vulnerability represents a critical concern for WordPress installations that rely on this plugin for custom content management, as it enables authenticated attackers to perform unauthorized actions on behalf of legitimate users.
The technical implementation of this vulnerability stems from improper validation and sanitization of data entered into custom field parameters within the plugin's administrative interface. When editors or administrators create or modify custom fields, the plugin fails to adequately escape or filter special characters in field names, descriptions, or configuration values before rendering them in HTML output contexts. This oversight creates an environment where malicious actors can inject JavaScript payloads that execute when other users view the affected pages or edit forms. The vulnerability specifically manifests when user-supplied data containing script tags or other malicious code is processed without proper HTML escaping mechanisms, allowing the injected code to persist and execute in the browser context of other users.
The operational impact of CVE-2019-11871 extends beyond simple script execution, as it can enable attackers to perform a wide range of malicious activities including session hijacking, data exfiltration, and privilege escalation within the WordPress environment. An attacker with editor or administrator access could leverage this vulnerability to steal cookies, modify content, create new user accounts, or even install malware through the compromised administrative interface. The attack surface is particularly concerning given that editors and administrators typically have elevated privileges within WordPress systems, making successful exploitation potentially devastating for organizations relying on the plugin for content management. The vulnerability also aligns with CWE-79 which specifically addresses cross-site scripting flaws, and can be mapped to ATT&CK technique T1059.007 for command and scripting interpreter usage through malicious script injection.
Organizations should immediately implement mitigations including upgrading to Custom Field Suite plugin version 2.5.15 or later, which contains the necessary patches to address the XSS vulnerability. Additionally, administrators should conduct thorough security audits of their WordPress installations to identify any other potentially vulnerable plugins or themes that might exhibit similar sanitization issues. Network monitoring should be enhanced to detect unusual patterns of script injection attempts, while access controls should be strictly enforced to limit the number of users with editor or administrator privileges. Regular security scanning and penetration testing of WordPress environments can help identify similar vulnerabilities in other components, and implementing Content Security Policy headers can provide additional defense-in-depth measures against script execution. The vulnerability also highlights the importance of proper input validation and output escaping practices in web application development, emphasizing the need for comprehensive security testing throughout the software development lifecycle to prevent similar issues in other WordPress plugins and themes.