CVE-2024-9651 in Fluent Forms Plugin
Summary
by MITRE • 12/09/2024
The Fluent Forms WordPress plugin before 5.2.1 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).
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Analysis
by VulDB Data Team • 05/07/2025
The vulnerability identified as CVE-2024-9651 affects the Fluent Forms WordPress plugin version 5.2.1 and earlier, presenting a significant security risk through stored cross-site scripting flaws. This issue specifically targets high-privilege users such as administrators who possess the unfiltered_html capability, though the vulnerability remains exploitable even when this capability is restricted, particularly in multisite WordPress environments where security controls may be more complex. The flaw stems from inadequate sanitization and escaping of user-provided input within the plugin's settings management functionality.
The technical implementation of this vulnerability resides in the plugin's failure to properly validate and sanitize data entered through its administrative interfaces. When administrators configure form settings or input data within the Fluent Forms plugin, the system does not adequately filter or escape potentially malicious content that could contain script tags or other XSS payloads. This oversight allows attackers with administrative privileges to inject malicious scripts that persist within the plugin's settings storage, making the vulnerability a stored XSS threat rather than a reflected one. The vulnerability is particularly concerning because it operates even when WordPress security measures such as the unfiltered_html capability restriction are in place, which typically prevents untrusted users from submitting raw HTML content.
The operational impact of this vulnerability extends beyond simple data corruption or display issues, as it can enable attackers to execute arbitrary JavaScript code within the context of an administrator's browser session. This capability allows for session hijacking, privilege escalation, and potential lateral movement within the compromised WordPress environment. In a multisite setup, the implications are even more severe as the vulnerability could affect multiple sites within the network, potentially enabling attackers to compromise the entire multisite installation. The stored nature of the vulnerability means that malicious scripts persist indefinitely until manually removed by administrators, making detection and remediation more challenging.
Security professionals should note this vulnerability aligns with CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') and relates to ATT&CK technique T1548.005 - Server Software Component Compromise, as it represents an attack vector through compromised administrative interfaces. Organizations should immediately update to Fluent Forms version 5.2.1 or later, which includes proper sanitization and escaping mechanisms for user inputs. Additionally, implementing network-based monitoring solutions to detect suspicious administrative activities and regular security audits of plugin configurations can help identify potential exploitation attempts. The vulnerability demonstrates the critical importance of input validation and output escaping in web applications, particularly within content management systems where administrative interfaces handle user-provided data.