CVE-2026-11881 in Fluent Forms Plugin
Summary
by MITRE • 07/30/2026
The Fluent Forms WordPress plugin before 6.2.6 does not sanitise and escape one of its form field configuration settings before outputting it inside an inline script when a form is rendered, which could allow users with a role as low as Contributor (with delegated form-management permission, and therefore lacking the unfiltered_html capability, e.g. in a multisite setup) to perform Stored Cross-Site Scripting attacks that execute in the browser of any visitor who loads the form, including administrators previewing it.
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Analysis
by VulDB Data Team • 07/30/2026
The vulnerability identified in Fluent Forms WordPress plugin versions prior to 6.2.6 represents a critical stored cross-site scripting flaw that exploits insufficient input sanitization and output escaping mechanisms within the plugin's form field configuration handling. This security weakness specifically targets the inline script generation process where form field settings are directly embedded into JavaScript code without proper sanitization, creating an attack vector that can be exploited by users with minimal privileges.
The technical implementation of this vulnerability stems from the plugin's failure to properly sanitize user-supplied data before incorporating it into dynamically generated JavaScript code. When a form is rendered, the plugin outputs configuration settings directly within inline script tags, creating a scenario where malicious payloads can persist in the database and execute whenever the form is loaded. This stored XSS vulnerability operates at the contributor level, meaning even users without the unfiltered_html capability can exploit this flaw through delegated form management permissions, particularly in multisite environments where such permissions might be granted without full administrative privileges.
The operational impact of this vulnerability extends beyond simple script execution, as it affects all visitors who load the affected forms including administrators who preview them. This creates a significant risk escalation scenario where an attacker with contributor-level access can potentially execute malicious code in the context of any user's browser session, including those of privileged administrators. The stored nature of the vulnerability means that once a malicious payload is injected into the form configuration, it persists indefinitely until manually removed by an administrator, making it particularly dangerous for long-running websites or frequently used forms.
This vulnerability aligns with CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') and follows ATT&CK technique T1566.001 - Phishing: Spearphishing Attachment, as it enables attackers to craft malicious form configurations that can be delivered to users through legitimate website interactions. The attack chain begins with a low-privilege user creating or modifying form fields containing malicious JavaScript payloads, which then executes in the browser context of any visitor who encounters the form, potentially leading to session hijacking, credential theft, or further exploitation of the compromised browser environment.
Mitigation strategies should include immediate upgrading to Fluent Forms version 6.2.6 or later, which implements proper sanitization and escaping of form field configuration data before outputting it in inline scripts. Administrators should also implement additional security measures such as restricting contributor-level access to form management capabilities where possible, implementing content security policies to limit script execution contexts, and regularly auditing form configurations for suspicious payloads. The vulnerability demonstrates the importance of input validation and output escaping at every level of web application development, particularly when dealing with user-generated content that gets rendered in dynamic contexts where it could be executed as code by other users.