CVE-2025-14436: Brevo for WooCommerce XSS Vulnerability

CVE-2025-14436 Overview

The Brevo for WooCommerce plugin for WordPress contains a Stored Cross-Site Scripting (XSS) vulnerability in the user_connection_id parameter. This security flaw affects all versions up to and including 4.0.49 and stems from insufficient input sanitization and output escaping. The vulnerability enables unauthenticated attackers to inject arbitrary web scripts into WordPress pages, which execute whenever a user accesses an affected page.

Critical Impact

Unauthenticated attackers can inject persistent malicious scripts that execute in the browsers of all users viewing affected pages, potentially leading to session hijacking, credential theft, or website defacement.

Affected Products

• Brevo for WooCommerce plugin version 4.0.49 and earlier
• WordPress sites using the WooCommerce Sendinblue Newsletter Subscription plugin
• All WordPress installations with the vulnerable plugin versions active

Discovery Timeline

• 2026-01-08 - CVE CVE-2025-14436 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2025-14436

Vulnerability Analysis

This Stored Cross-Site Scripting vulnerability exists within the Brevo for WooCommerce plugin's handling of the user_connection_id parameter. The plugin fails to properly sanitize user-supplied input and escape output when rendering this parameter value in the WordPress administrative interface and potentially other page contexts.

When the user_connection_id parameter is processed, the plugin stores the unsanitized value in the database. Subsequently, when pages containing this stored value are rendered, the malicious script payload executes in the context of the victim's browser session. This is particularly dangerous because the vulnerability requires no authentication to exploit, significantly lowering the barrier for attackers.

The vulnerability affects multiple files within the plugin's codebase, including the admin manager (admin-manager.php), admin menu views (admin_menus.php), and the main plugin file (woocommerce-sendinblue.php). The attack surface spans user connection management functionality where input validation should occur but is insufficient.

Root Cause

The root cause of CVE-2025-14436 is the absence of proper input sanitization and output escaping mechanisms when handling the user_connection_id parameter. WordPress provides built-in sanitization functions such as sanitize_text_field() for input and esc_html() or esc_attr() for output escaping, but the vulnerable code paths do not adequately implement these security controls.

The vulnerability exists because user-supplied data flows from input to storage to output without being properly validated or encoded, violating secure coding principles for web application development.

Attack Vector

The attack is executed over the network and requires no authentication or user interaction for the initial payload injection. An attacker can craft a malicious HTTP request containing JavaScript payloads within the user_connection_id parameter. Once stored, the payload persists in the WordPress database and executes automatically when any user (including administrators) views a page that renders the affected data.

A typical attack scenario involves an attacker submitting a crafted request that includes JavaScript code within the vulnerable parameter. The malicious script might be designed to steal session cookies, redirect users to phishing sites, modify page content, or perform actions on behalf of authenticated administrators.

Detection Methods for CVE-2025-14436

Indicators of Compromise

• Unexpected JavaScript code or HTML tags stored in database fields associated with the Brevo/Sendinblue plugin
• Suspicious entries in web server access logs showing attempts to inject script tags via POST or GET parameters
• Browser developer console errors or unexpected script execution warnings when accessing WooCommerce or plugin administration pages
• Reports from users of unexpected browser behavior or redirects when visiting the WordPress site

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to detect and block XSS payload patterns in HTTP requests targeting WordPress plugin endpoints
• Implement Content Security Policy (CSP) headers to restrict inline script execution and provide violation reporting
• Use WordPress security plugins that monitor for stored XSS indicators and unauthorized script modifications
• Conduct regular database audits to identify suspicious content containing script tags or event handlers

Monitoring Recommendations

• Enable detailed logging for all POST requests to WordPress administrative endpoints and plugin-specific URLs
• Monitor for CSP violation reports that may indicate attempted or successful XSS exploitation
• Set up alerts for new or modified database entries containing potentially malicious patterns such as <script>, javascript:, or event handler attributes
• Review browser-side security headers to ensure proper XSS protection mechanisms are in place

How to Mitigate CVE-2025-14436

Immediate Actions Required

• Update the Brevo for WooCommerce plugin to a patched version newer than 4.0.49 immediately
• Review and audit the WordPress database for any previously injected malicious scripts in plugin-related tables
• Implement a Web Application Firewall with XSS filtering capabilities to provide an additional layer of protection
• Consider temporarily disabling the plugin if an immediate update is not possible until a secure version can be applied

Patch Information

A patch for this vulnerability has been released by the plugin developers. The WordPress Plugin Changeset contains the security fix addressing the improper input handling. Site administrators should update through the WordPress plugin update mechanism or manually download the patched version from the WordPress plugin repository.

For detailed vulnerability information, refer to the Wordfence Vulnerability Details page.

Workarounds

• Implement Content Security Policy headers with strict script-src directives to mitigate the impact of injected scripts until a patch can be applied
• Use a WAF rule to filter and block requests containing common XSS payloads targeting the plugin's endpoints
• Restrict access to the WordPress administrative interface to trusted IP addresses only
• Disable the Brevo for WooCommerce plugin temporarily if the functionality is not critical to business operations

# Example CSP header configuration for Apache (.htaccess)
Header set Content-Security-Policy "default-src 'self'; script-src 'self' https://trusted-cdn.example.com; object-src 'none'; base-uri 'self';"