CVE-2025-23556: Push Envoy Notifications XSS Vulnerability

CVE-2025-23556 Overview

CVE-2025-23556 is a Reflected Cross-Site Scripting (XSS) vulnerability affecting the Push Envoy Notifications WordPress plugin developed by netbitsolutions. This vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing attackers to inject malicious scripts that execute in the context of a victim's browser session.

Reflected XSS vulnerabilities occur when user input is immediately returned by a web application in an error message, search result, or other response without proper sanitization. In the case of Push Envoy Notifications, malicious actors can craft specially designed URLs containing JavaScript payloads that execute when clicked by unsuspecting users.

Critical Impact

Attackers can steal session cookies, perform actions on behalf of authenticated users, redirect victims to malicious sites, or deface web pages by exploiting this reflected XSS vulnerability.

Affected Products

• Push Envoy Notifications WordPress Plugin version 1.0.0 and earlier
• WordPress installations with the push-envoy plugin enabled
• All sites using vulnerable versions without input sanitization patches

Discovery Timeline

• 2025-03-03 - CVE-2025-23556 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-23556

Vulnerability Analysis

This vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The Push Envoy Notifications plugin fails to properly sanitize user-supplied input before reflecting it back in the HTTP response.

The vulnerability allows attackers to inject arbitrary JavaScript code that executes within the security context of the vulnerable website. When a victim clicks on a malicious link containing the XSS payload, the injected script runs with the same privileges as legitimate scripts on the page, potentially compromising user sessions and sensitive data.

WordPress plugins that handle user notifications are particularly attractive targets because they often process user-controlled parameters for customization and display purposes. Without proper output encoding or input validation, these parameters become vectors for script injection attacks.

Root Cause

The root cause of this vulnerability is insufficient input validation and output encoding in the Push Envoy Notifications plugin. When the plugin processes user-supplied parameters, it fails to neutralize special characters such as <, >, ", and ' that have special meaning in HTML and JavaScript contexts.

Proper remediation requires implementing context-aware output encoding (HTML entity encoding for HTML contexts, JavaScript encoding for script contexts) and validating all user inputs against an allowlist of expected values before processing.

Attack Vector

The attack vector for this reflected XSS vulnerability involves crafting a malicious URL containing JavaScript payloads in vulnerable parameters. The attacker must then convince a victim to click the link, typically through phishing emails, social engineering, or embedding the link in forum posts or comments.

When the victim clicks the malicious link, their browser sends a request to the vulnerable WordPress site. The server processes the request and reflects the unsanitized payload back in the response. The victim's browser then executes the malicious script, believing it to be legitimate content from the trusted website.

The vulnerability does not require authentication, meaning any visitor to the site can be targeted. However, attacks targeting authenticated administrators or users with elevated privileges pose the greatest risk, as successful exploitation could lead to session hijacking or administrative account takeover.

Detection Methods for CVE-2025-23556

Indicators of Compromise

• Unusual URL parameters containing encoded JavaScript payloads (e.g., %3Cscript%3E, javascript:, onerror=)
• Web server logs showing requests with suspicious query strings targeting the Push Envoy plugin endpoints
• User reports of unexpected browser behavior or redirects after clicking links related to the WordPress site
• Evidence of cookie theft attempts or unauthorized session activity

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block common XSS patterns in URL parameters
• Deploy browser-based Content Security Policy (CSP) headers to prevent inline script execution
• Monitor access logs for requests containing common XSS attack signatures targeting plugin directories
• Use automated vulnerability scanners to identify unpatched WordPress plugins

Monitoring Recommendations

• Enable detailed logging for all requests to WordPress plugin endpoints
• Configure alerts for unusual patterns of encoded characters in URL parameters
• Monitor for JavaScript errors or unexpected script execution in browser developer tools
• Review referrer headers for suspicious external sources linking to your WordPress installation

How to Mitigate CVE-2025-23556

Immediate Actions Required

• Update the Push Envoy Notifications plugin to the latest patched version when available
• Consider temporarily disabling the push-envoy plugin if a patch is not yet available
• Implement a Web Application Firewall with XSS protection rules
• Add Content Security Policy headers to restrict inline script execution

Patch Information

Administrators should monitor the Patchstack WordPress Vulnerability Report for updates regarding security patches. Until an official fix is released, site administrators should implement defensive measures to protect users from exploitation.

Plugin updates can be applied through the WordPress admin dashboard under Plugins > Installed Plugins, or by manually downloading and replacing the plugin files via FTP/SFTP.

Workarounds

• Disable the Push Envoy Notifications plugin until a security patch is available
• Implement strict Content Security Policy headers to block inline script execution
• Deploy a WAF rule to filter requests containing XSS payloads targeting the plugin
• Restrict access to WordPress admin areas using IP allowlisting or VPN requirements

# WordPress .htaccess configuration to add basic XSS protection headers
<IfModule mod_headers.c>
    Header set X-XSS-Protection "1; mode=block"
    Header set X-Content-Type-Options "nosniff"
    Header set Content-Security-Policy "default-src 'self'; script-src 'self';"
</IfModule>