CVE-2024-4043 in WP Ultimate Post Grid Plugin
Summary
by MITRE • 05/23/2024
The WP Ultimate Post Grid plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's 'wpupg-text' shortcode in all versions up to, and including, 3.9.1 due to insufficient input sanitization and output escaping on user supplied attributes. 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 • 03/28/2025
The WP Ultimate Post Grid plugin represents a widely used WordPress solution for displaying content in grid layouts, making it a critical component in many website architectures. This particular vulnerability exists within the plugin's 'wpupg-text' shortcode implementation, which allows administrators to embed dynamic text content into posts and pages. The flaw manifests as a stored cross-site scripting vulnerability that affects all versions up to and including 3.9.1, creating a persistent security risk for WordPress installations that utilize this functionality. Attackers exploiting this weakness can inject malicious scripts that execute whenever users view affected pages, potentially leading to widespread compromise across the affected website's user base.
The technical root cause of this vulnerability stems from inadequate input sanitization and output escaping mechanisms within the plugin's codebase. When users supply attributes to the 'wpupg-text' shortcode, the plugin fails to properly validate or escape these inputs before storing them in the database. This insufficient sanitization creates an environment where malicious payloads can be persistently stored and later executed without proper validation. The vulnerability specifically targets user-supplied attributes that are processed through the shortcode system, making it particularly dangerous because these attributes can contain HTML content that gets rendered in the final output. According to CWE-79, this represents a classic stored cross-site scripting flaw where malicious scripts are permanently stored on the server and executed when accessed by other users.
The operational impact of this vulnerability extends beyond simple script execution, as authenticated attackers with contributor-level privileges or higher can leverage this weakness to perform various malicious activities. Once an attacker gains access through this vector, they can inject persistent malware payloads that target unsuspecting visitors, potentially leading to credential theft, session hijacking, or redirection to malicious sites. The stored nature of the vulnerability means that even if administrators later patch the plugin, previously injected scripts continue to execute until manually removed from the database. This makes the attack particularly insidious as it can remain undetected for extended periods while continuously compromising user sessions and data.
Security professionals should implement immediate mitigations including upgrading to patched versions of the WP Ultimate Post Grid plugin where available, though in this case no patch exists beyond version 3.9.1. Organizations must also consider implementing additional protective measures such as input validation at the web application firewall level, regular database scanning for malicious content, and monitoring user activity for unauthorized shortcode modifications. The vulnerability demonstrates the critical importance of proper input sanitization and output escaping practices in web applications, aligning with ATT&CK technique T1566.001 for initial access through malicious content. Additionally, this weakness highlights the need for comprehensive security testing including dynamic analysis of shortcode implementations and user input handling mechanisms to prevent similar issues from occurring in other plugins or custom WordPress themes.
Organizations should also conduct thorough audits of their WordPress installations to identify all instances where similar vulnerabilities might exist within other plugins or themes. The presence of such stored XSS vulnerabilities often indicates broader architectural weaknesses in how applications handle user-supplied content, making it essential to establish robust input validation policies and output encoding practices across all web applications. Regular security assessments including penetration testing and code review processes are crucial for identifying and remediating these types of vulnerabilities before they can be exploited by malicious actors. The vulnerability serves as a reminder that even seemingly benign features like text display shortcodes can become attack vectors when proper security controls are not implemented in the development lifecycle.