In this post, we'll be discussing the vulnerability identified as CVE-2023-1405 which affects the Formidable Forms WordPress plugin before version 6.2. We will explain the vulnerability, how it can be exploited, and offer recommendations for keeping your website secure. A code snippet and links to original references will be provided for further understanding.

Vulnerability Description

The vulnerability within the Formidable Forms WordPress plugin before 6.2 stems from improper handling of user input, specifically the unserialization of data from users. This security flaw allows anonymous users to perform a PHP Object Injection by providing a suitable gadget (i.e., PHP class with a magic method) within the user input. Armed with the power of PHP Object Injection, a malicious user could execute arbitrary code on the targeted system, potentially leading to unauthorized access, data leakage, and more.

Exploit Details

A PHP Object Injection occurs when an attacker manages to instantiate arbitrary objects within an application by providing a serialized representation of that object within their input. In the case of the Formidable Forms plugin, the unserialization of user data allows for this type of attack.

Here is a simplified example of a code snippet demonstrating the vulnerability

class Example {
    public $payload;

    public function __wakeup() {

$userData = $_POST['data'];
$unserializedData = unserialize($userData);

In this example, when the plugin unserializes user data without sanitizing it, anyone providing a serialized instance (in this case, an instance of "Example") can cause the server to execute arbitrary code provided within the "payload" attribute through the "eval()" function.

To exploit this vulnerability, an attacker would craft a serialized object containing the PHP code they want to execute and submit it as input via a specially crafted POST request. The vulnerable server would unserialize the data, creating an instance of the object, and the code defined within the "payload" attribute would execute.


The best way to mitigate this vulnerability and prevent PHP Object Injection is to update the Formidable Forms WordPress plugin to the latest version (6.2 or higher), as the plugin developers have addressed this specific issue in the updated version.

It is also essential to ensure only trusted users can submit input to your application and make sure user input is appropriately sanitized and validated.

For additional information on CVE-2023-1405, you can refer to the following resources

- CVE Details:
- NVD:


In summary, CVE-2023-1405 is a critical vulnerability in the Formidable Forms WordPress plugin that allows remote attackers to exploit the PHP Object Injection flaw and potentially execute arbitrary code on the server. It is vital to update your plugin to the latest version (6.2 or higher) and properly sanitize and validate user input to prevent unauthorized access and ensure your website's continued security.


Published on: 01/16/2024 16:15:10 UTC
Last modified on: 01/23/2024 14:28:58 UTC