CVE-2024-3559 in Custom Field Suite Plugin
Summary
by MITRE • 06/12/2024
The Custom Field Suite plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the the 'cfs[post_content]' parameter versions up to, and including, 2.6.7 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
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Analysis
by VulDB Data Team • 03/24/2025
The Custom Field Suite plugin for WordPress represents a widely used tool for extending content management capabilities within the WordPress ecosystem. This particular vulnerability affects versions up to and including 2.6.7, creating a significant security risk for WordPress installations that rely on this plugin for custom field management. The vulnerability manifests through improper handling of user input within the plugin's processing logic, specifically affecting the 'cfs[post_content]' parameter which is used to manage content fields within the plugin's interface.
The technical flaw stems from insufficient input sanitization and output escaping mechanisms within the plugin's codebase. When authenticated users with contributor-level access or higher submit content through the affected parameter, the plugin fails to properly validate or sanitize the input before storing it in the database. This allows malicious actors to inject malicious scripts that are subsequently executed whenever any user accesses pages containing the stored malicious content. The vulnerability operates as a classic stored cross-site scripting attack where the malicious payload is persisted server-side rather than being reflected in HTTP responses.
The operational impact of this vulnerability is substantial as it requires only contributor-level privileges to exploit, which is a relatively low access level within WordPress's user permission structure. This means that attackers who have gained access to a contributor account or higher can leverage this vulnerability to compromise other users within the same WordPress installation. The attack vector is particularly dangerous because it can affect any user who accesses pages containing the malicious content, potentially leading to session hijacking, credential theft, or further exploitation of the compromised WordPress environment.
From a cybersecurity perspective, this vulnerability aligns with CWE-79 - Improper Neutralization of Input During Web Page Generation, which specifically addresses cross-site scripting issues. The weakness can be mapped to ATT&CK technique T1566.001 - Phishing: Spearphishing Attachment, as attackers could potentially use this vulnerability to deliver malicious payloads through compromised WordPress content. Additionally, the vulnerability demonstrates characteristics of T1071.001 - Application Layer Protocol: Web Protocols, as it exploits web application functionality to execute malicious code.
Organizations should immediately update to the latest version of the Custom Field Suite plugin where this vulnerability has been addressed. Administrators should also implement additional monitoring of user activities and content submissions within WordPress environments. The mitigation strategy should include regular security audits of installed plugins, implementation of web application firewalls, and enforcement of strict content validation policies. Security teams should also consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities. Regular vulnerability scanning and penetration testing should be conducted to identify similar issues in other plugins and themes that may present similar security risks.