Formidable Forms <= 6.0.1 - IP Spoofing via HTTP header

Reliance on Untrusted Inputs in a Security Decision
CVE CVE-2023-0816
CVSS 5.3 (Medium)
Publicly Published March 6, 2023
Last Updated January 22, 2024
Researcher Daniel Ruf


The Formidable Forms plugin for WordPress is vulnerable to IP Spoofing in versions up to, and including, 6.0.1 due to a reliance on various untrusted headers (e.g., 'Client-Ip', 'CF-CONNECTING-IP', etc.) to retrieve the IP address of a client performing a form submission. This makes it possible for unauthenticated users to bypass the plugin's anti-spam protections.



Vulnerability Details for Formidable Forms – Contact Form Plugin, Survey, Quiz, Payment, Calculator Form & Custom Form Builder

Software Type Plugin
Software Slug formidable (view on
Patched? Yes
Remediation Update to version 6.1, or a newer patched version
Affected Version
  • <= 6.0.1
Patched Version
  • 6.1

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