CVE-2023-5387 in Funnelforms Free Plugin
Summary
by MITRE • 11/22/2023
The Funnelforms Free plugin for WordPress is vulnerable to unauthorized modification of data due to a missing capability check on the fnsf_af2_trigger_dark_mode function in versions up to, and including, 3.4. This makes it possible for authenticated attackers, with subscriber-level permissions and above, to enable or disable the dark mode plugin setting.
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Analysis
by VulDB Data Team • 04/11/2026
The Funnelforms Free plugin for WordPress represents a widely used tool for creating and managing web forms within the WordPress ecosystem. This particular vulnerability affects versions up to and including 3.4, where a critical security flaw exists in the plugin's access control mechanisms. The vulnerability manifests specifically within the fnsf_af2_trigger_dark_mode function, which handles the toggling of dark mode settings for the plugin interface. This function lacks proper capability checks that would normally verify whether the requesting user possesses sufficient privileges to modify plugin configurations.
The technical flaw stems from a missing capability verification within the WordPress plugin architecture, which directly violates established security principles for access control. In WordPress, different user roles possess varying levels of permissions, and certain administrative functions should only be accessible to users with appropriate capabilities such as administrators or editors. The absence of this capability check creates an unauthorized access vector where users with subscriber-level permissions or higher can manipulate plugin settings without proper authorization. This represents a classic privilege escalation vulnerability that allows attackers to perform actions beyond their intended permissions.
The operational impact of this vulnerability extends beyond simple configuration changes, as it enables authenticated attackers to potentially disrupt user experience and compromise the intended functionality of the plugin. Attackers with subscriber-level access can toggle dark mode settings at will, which may serve as a stepping stone for further exploitation or simply cause confusion for end users. The vulnerability is particularly concerning because it requires minimal privileges to exploit, making it accessible to users who should not have the ability to modify core plugin behavior. This weakness could potentially be leveraged as part of a broader attack chain, where attackers first establish a foothold with subscriber permissions before escalating their privileges through additional vulnerabilities.
From a cybersecurity perspective, this vulnerability aligns with CWE-284, which addresses improper access control, and represents a clear violation of the principle of least privilege. The ATT&CK framework categorizes this as a privilege escalation technique where attackers exploit missing access controls to gain elevated permissions within the system. Organizations using this plugin should immediately implement mitigation strategies including updating to the latest version where the capability check has been properly implemented. Additionally, administrators should review user roles and permissions to ensure that subscribers and other lower-level users do not possess unnecessary capabilities that could be exploited in similar vulnerabilities. The vulnerability demonstrates the critical importance of implementing proper access control mechanisms in all plugin and theme code, as even seemingly minor functionality can create significant security risks when implemented without adequate security checks.