CVE-2025-23602: EELV Newsletter Reflected XSS Vulnerability

CVE-2025-23602 Overview

CVE-2025-23602 is a Reflected Cross-Site Scripting (XSS) vulnerability affecting the EELV Newsletter WordPress plugin developed by Europe Ecologie Les Verts. The vulnerability stems from improper neutralization of user 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 an application includes unvalidated user-supplied data in its HTTP responses. In this case, the EELV Newsletter plugin fails to properly sanitize input before reflecting it back to users, creating an opportunity for attackers to craft malicious URLs that, when clicked by authenticated users, execute arbitrary JavaScript code.

Critical Impact

Attackers can execute malicious scripts in victim browsers, potentially stealing session cookies, redirecting users to phishing sites, or performing unauthorized actions on behalf of authenticated WordPress administrators.

Affected Products

• EELV Newsletter WordPress Plugin versions up to and including 4.8.2
• WordPress installations using vulnerable EELV Newsletter plugin versions

Discovery Timeline

• 2025-01-22 - CVE-2025-23602 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2025-23602

Vulnerability Analysis

This vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), which encompasses Cross-Site Scripting flaws. The EELV Newsletter plugin fails to implement proper input validation and output encoding when processing user-supplied data, allowing malicious JavaScript to be reflected back to users in the HTTP response.

Reflected XSS attacks typically require social engineering to trick victims into clicking specially crafted links. Once a victim clicks a malicious URL containing the XSS payload, the script executes within their browser session with the same privileges as the legitimate application. For WordPress administrators, this could result in complete site compromise.

The vulnerability affects all versions of the EELV Newsletter plugin through 4.8.2, indicating that the input sanitization issue exists in the core functionality of the plugin and has persisted across multiple releases.

Root Cause

The root cause of this vulnerability is insufficient input validation and output encoding within the EELV Newsletter plugin. When user-controlled data is included in HTTP responses without proper sanitization or encoding, browsers interpret the malicious input as legitimate script code rather than data.

WordPress plugins are expected to use built-in sanitization functions such as esc_html(), esc_attr(), wp_kses(), and similar functions to prevent XSS attacks. The absence or improper use of these security controls in the EELV Newsletter plugin allows attackers to bypass the expected security boundary between data and code.

Attack Vector

The attack vector for this Reflected XSS vulnerability involves crafting a malicious URL containing JavaScript payload in a vulnerable parameter. The attacker then distributes this URL through phishing emails, social media, or other channels to potential victims.

When a victim clicks the malicious link, the vulnerable plugin reflects the attacker's payload in the response without proper encoding. The victim's browser then executes the injected JavaScript, which can perform actions such as stealing authentication cookies, modifying page content, or redirecting to malicious sites.

For detailed technical information about this vulnerability, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2025-23602

Indicators of Compromise

• Unusual URL parameters containing encoded JavaScript or HTML tags in requests to EELV Newsletter plugin endpoints
• Web server logs showing suspicious requests with <script> tags or event handlers like onerror, onload in query strings
• Browser developer console errors indicating blocked inline scripts (if CSP is enabled)
• Reports from users of unexpected redirects or strange behavior when interacting with newsletter functionality

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to detect and block requests containing XSS patterns targeting the EELV Newsletter plugin
• Implement Content Security Policy (CSP) headers to prevent inline script execution and detect violation attempts
• Review web server access logs for requests with suspicious URL-encoded characters such as %3Cscript%3E or javascript: in newsletter-related endpoints
• Utilize WordPress security plugins that monitor for XSS attack patterns

Monitoring Recommendations

• Enable detailed logging for all requests to WordPress plugin endpoints, particularly /wp-content/plugins/eelv-newsletter/
• Configure alerting for requests containing common XSS patterns in URL parameters
• Monitor for unusual spikes in requests to newsletter functionality that may indicate automated exploitation attempts
• Review user reports of unexpected behavior or visual anomalies on pages using the newsletter plugin

How to Mitigate CVE-2025-23602

Immediate Actions Required

• Review current EELV Newsletter plugin version and determine if your installation is affected (versions 4.8.2 and below are vulnerable)
• Consider temporarily disabling the EELV Newsletter plugin if it is not business-critical until a patch is available
• Implement a Web Application Firewall with XSS protection rules to filter malicious requests
• Add Content Security Policy headers to reduce the impact of potential XSS exploitation
• Educate users about the risks of clicking suspicious links, particularly those targeting WordPress administrative functions

Patch Information

At the time of this writing, users should monitor the Patchstack Vulnerability Report for updates on patch availability. Organizations should upgrade to the latest version of the EELV Newsletter plugin once a security fix is released.

WordPress administrators should ensure automatic plugin updates are enabled and regularly audit installed plugins for known vulnerabilities using tools like WPScan or Patchstack.

Workarounds

• Temporarily deactivate the EELV Newsletter plugin if newsletter functionality is not immediately required
• Implement strict Content Security Policy headers to prevent inline script execution: Content-Security-Policy: script-src 'self'; object-src 'none';
• Deploy WAF rules to block requests containing common XSS payloads targeting the plugin
• Restrict access to WordPress admin areas using IP whitelisting or VPN requirements
• Consider using an alternative newsletter plugin that has been audited for security vulnerabilities

# Add CSP headers in Apache .htaccess
Header set Content-Security-Policy "script-src 'self'; object-src 'none';"

# Or in Nginx configuration
add_header Content-Security-Policy "script-src 'self'; object-src 'none';";