Exploiting User Registration and Membership Logic for Privilege Escalation (CVE-2025-2563)

As defenders patch vulnerabilities in production environments, threat actors continually adapt to exploit new weaknesses, sometimes for financial gain and sometimes to disrupt operations. In this blog, we'll explore how attackers can escalate privileges via a web GUI and ultimately obtain shell access by exploiting a recently disclosed WordPress vulnerability, CVE-2025-2563.

We'll walk through the attack chain from an attacker’s perspective against a practice (non-production) WordPress website, showing manual testing steps and demonstrating how the flaw can be abused.

Disclaimer: This guide is intended for educational purposes only. Do not attempt to replicate any techniques shown here in production environments or in environments for which you do not have explicit authorization, doing so is illegal. Always conduct security testing in a controlled and isolated environment with prior written permission.

Web GUI approach

For this demonstration, I relied on information from WPScan, which was extremely helpful in understanding the exploit. The first step is to set up a local or isolated test WordPress environment where the vulnerability can be safely reproduced. Before continuing, confirm that the test site is reachable (for example, by pinging its IP address or domain). In my case, I couldn’t initially reach the site, so I temporarily modified my network configuration to restore connectivity.

Note: always use an isolated test environment (snapshots or disposable VMs are recommended) and never test against production systems or systems for which you do not have explicit authorization.

Once the site is accessible:

1. Navigate to the Membership Pricing tab and register as a new user.

   

2. Complete the registration form with any basic details and submit it. You should receive a confirmation message.

   

3. After registration, return to the Membership Pricing tab.

4. Right-click on the page, open the browser's developer tools (Inspect), and go to the Console tab.

5. Modify the JavaScript payload (from the WPScan documentation) to include the username you just registered with. I did have to modify the payload due to it not working for some reason. I used online resources and ChatGPT to get the payload below.

6. To locate the ID, I first right clicked on “Page Source” on the same page of the Thank you page after you signed up. Then Click on the “Elements” tab and do Ctrl+f and search for either “membership”, “membership_id”, “members_data”, or the literal plugin name.

Look for things like:

7. <input type="hidden" name="membership" value="123">

   

8. Paste the edited payload into the console and press Enter.

9. If successful, you should see a message like: "New member has been successfully created."

   
   

You can now log in using the credentials you registered with. If a User tab appears in the sidebar, check it. You should see that your account has been elevated to an Administrator role. 

This confirms the privilege escalation vulnerability.

Part II of Web GUI Approach

Once you are logged in, you will see the admin WordPress page.

In order to get to the shell, you will need to be able to upload a .zip file into the plugins and have Netcat listening in on a specific port almost acting like a server of its own to report back to.

First create a new directory using an appropriate plugin name, open it, create a PHP file with the same name, and paste the PHP code into that file. (Note: Always check your spelling and make sure the directory stays consistently the same, it won’t work because of those reasons):

Next, you will leave the directory you have created and zip it with this command:

It should be like the picture below.

After that, get your Netcat ready in the terminal.

Return to the WordPress page and go to the plugins tab and click on “Add New Plugin”.

Next, click on “Upload Plugin” and make sure to select the .zip file. You will then see a message saying that it was successful.

Check your terminal and you should have gotten into the shell.

Non-admin approach

Since we already have a WordPress account, we can use the profile picture upload feature to demonstrate a basic PHP shell upload technique. The idea is to disguise our PHP shell as a .JPG file, because WordPress allows image uploads through the profile section for non-admin users. Admin privileges are not required for this demonstration; a regular Subscriber account will do. For this walkthrough, I created a user named Tubby, a standard Subscriber on the site.

The first step is to download a .JPG or .JPEG image from Google and save it to any directory of your choice. Next, I created a PHP shell named “2shell.php” to initiate a call back to my Netcat listener:

Next, I created a polyglot file, a file that can be interpreted as more than one file type; for this case, both an image and a PHP script. I created it using the following terminal command:

This command appends the PHP shell to the end of the image file, creating a single file called “shell_polyglot.jpg” that still appears to be a valid image. After creating the file, I uploaded the polyglot image using the WordPress profile picture uploader. 

Before visiting the URL, I prepared to catch the reverse shell by opening a Netcat 

listener on my machine with:

If the polyglot file is set up correctly, Netcat should receive a connection enabling you to connect in like the picture below. Therefore, giving you shell access to the WordPress server. At that point, you’ll see a new directory appear in the terminal. 

This confirms that you've successfully gained command-line access to the server hosting the WordPress site. Although the account used is not an admin account, it can still access many directories on the system.

Remediations and Mitigation

1)      Update WordPress User Registration & Membership WordPress plugin to 4.1.2 or later.

2)      Ensure file upload handlers strictly validate MIME types and reject polyglot files that combine multiple file formats.

3)      Perform a security review of custom code to confirm that user input is properly sanitized and validated.

4)      Prevent execution of uploaded files by disabling PHP execution in the /wp-content uploads/ directory.

5)      Implement a Web Application Firewall (WAF) to block suspicious JavaScript payloads and detect abnormal role-assignment requests.

6)      Only install plugins from trusted sources. Avoid third-party or pirated plugins/themes, as these may contain hidden backdoors or privilege escalation code.

While these tactics and remediations are effective, it’s important to remember that cyberattacks are constantly evolving. Threat actors continue to find new ways to breach systems just as quickly as cybersecurity professionals develop defenses. Maintaining vigilance and regularly assessing your overall security posture are essential to staying ahead of the emerging threats.