CVE-2023-6953 in PDF Generator for Fluent Forms Plugin
Summary
by MITRE • 02/06/2024
The PDF Generator For Fluent Forms – The Contact Form Plugin plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the header, PDF body and footer content parameters in all versions up to, and including, 1.1.7 due to insufficient input sanitization and output escaping. This makes it possible for attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The exploitation level depends on who is granted the right to create forms by an administrator. This level can be as low as contributor, but by default is admin.
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Analysis
by VulDB Data Team • 04/11/2026
The vulnerability identified as CVE-2023-6953 affects the PDF Generator For Fluent Forms plugin, a WordPress extension that enables users to generate PDF documents from contact form submissions. This particular flaw represents a critical stored cross-site scripting vulnerability that exists within the plugin's handling of user-controllable input fields. The vulnerability impacts all versions up to and including 1.1.7, making it a widespread concern for WordPress administrators who have installed this plugin. The security flaw stems from inadequate input sanitization and insufficient output escaping mechanisms that fail to properly validate and sanitize user-provided content before it is stored and subsequently rendered in PDF documents.
The technical implementation of this vulnerability occurs within the plugin's processing of header, PDF body, and footer content parameters. When administrators or authorized users create forms with the plugin, they can specify content for these elements that gets stored in the WordPress database. The flaw allows malicious actors to inject malicious JavaScript code into these parameters, which then gets executed whenever the generated PDF documents are viewed or processed. This stored nature of the vulnerability means that the malicious code persists in the system and executes automatically whenever users access the affected pages, creating a persistent threat vector. The vulnerability is classified under CWE-79 as a cross-site scripting flaw, specifically involving the storage of malicious content that gets executed in the context of other users' browsers.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the ability to perform various malicious activities depending on the privileges of the compromised user. Given that the plugin's configuration allows contributors to create forms by default, the attack surface is significantly broadened, enabling lower-privilege users to potentially compromise higher-privileged accounts. Attackers could exploit this vulnerability to steal user sessions, redirect victims to malicious websites, or perform actions on behalf of compromised users. The severity of the impact increases when considering that the plugin operates within the WordPress ecosystem, potentially allowing attackers to escalate privileges or access additional system resources through the compromised form generation functionality. This vulnerability aligns with ATT&CK technique T1566.001 for initial access through malicious file or code execution and T1059.007 for command and scripting interpreter through JavaScript execution.
The mitigation strategy for CVE-2023-6953 requires immediate attention from WordPress administrators who have installed the affected plugin. The primary recommendation involves updating the plugin to the latest version where the vulnerability has been patched, as this addresses the core sanitization and escaping issues. Administrators should also review user permissions and restrict form creation capabilities to only trusted administrators, thereby reducing the attack surface. Implementing proper input validation and output escaping mechanisms at the application level provides additional defense-in-depth measures. Security monitoring should be enhanced to detect unusual form creation patterns or content that might indicate exploitation attempts. Additionally, implementing content security policies and regular security audits of WordPress plugins can help prevent similar vulnerabilities from being introduced into the system. Organizations should also consider implementing web application firewalls to detect and block malicious payloads attempting to exploit this type of vulnerability.