CVE-2025-11994: Easy Email Subscription XSS Vulnerability

CVE-2025-11994 Overview

CVE-2025-11994 is a Stored Cross-Site Scripting (XSS) vulnerability in the Easy Email Subscription plugin for WordPress. The flaw affects all plugin versions up to and including 1.3. The vulnerability stems from insufficient input sanitization and output escaping on the name parameter handled by the subscriber form. Unauthenticated attackers can inject arbitrary JavaScript that executes in any visitor's browser when an affected page renders the stored payload. The issue is tracked under [CWE-79] (Improper Neutralization of Input During Web Page Generation).

Critical Impact
Unauthenticated remote attackers can inject persistent JavaScript that executes against site administrators and visitors, enabling session theft, redirection, and administrative account takeover.

Affected Products

WordPress Easy Email Subscription plugin (slug: email-subscription-with-secure-captcha) versions up to and including 1.3
WordPress sites running vulnerable instances of simple-email-subscription.php
WordPress sites exposing the public subscriber form via subscriber-form.php

Discovery Timeline

2025-11-12 - CVE-2025-11994 published to NVD
2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-11994

Vulnerability Analysis

The vulnerability resides in how the Easy Email Subscription plugin processes the name field submitted through its subscriber form. The plugin accepts user-supplied input from an unauthenticated context and stores it without applying adequate sanitization routines such as sanitize_text_field(). When the stored value is later rendered in the WordPress admin or front-end views, the plugin emits the value without applying output escaping functions like esc_html() or esc_attr().

This combination allows attacker-controlled markup to persist in the database and execute in the browsers of users who view the affected page. The vulnerability requires no authentication and no user interaction beyond the victim loading an injected page. The exploit prediction scoring system places this issue in the lower probability tier, but the unauthenticated attack surface and persistent payload make opportunistic exploitation realistic for exposed sites.

Root Cause

The root cause is a missing sanitization-and-escaping pair in the subscription handling logic inside simple-email-subscription.php and the rendering path within subscriber-form.php. The plugin trusts the name parameter on input and reuses it on output, breaking the WordPress secure coding principle of late escaping. The vendor remediated the issue in changeset 3388578, which added proper input filtering and output escaping for subscriber fields.

Attack Vector

An unauthenticated attacker submits the subscription form with a crafted name value containing JavaScript markup, for example a <script> element or an event handler attribute. The malicious payload is stored in the WordPress database. Any administrator viewing the subscribers list, or any visitor loading a page that renders the stored value, triggers script execution in the same origin as the WordPress site. The cross-origin scope change enables the attacker to read session cookies that are not flagged HttpOnly, perform privileged actions through the admin's session, or pivot to deliver follow-on payloads.

Detection Methods for CVE-2025-11994

Indicators of Compromise

Subscriber records containing HTML tags, <script> elements, on* event-handler attributes, or javascript: URIs in the name column of the plugin's database table.
Outbound HTTP requests from administrator browsers to unknown domains immediately after visiting the WordPress admin subscribers view.
New or modified WordPress administrator accounts shortly after suspicious subscriber form submissions.

Detection Strategies

Query the WordPress database for stored subscriber names containing <, >, script, onerror, or onload substrings.
Inspect web server access logs for POST requests to subscription endpoints with payloads containing URL-encoded HTML or JavaScript.
Enable a Web Application Firewall (WAF) signature for stored XSS attempts targeting WordPress plugin subscription forms.

Monitoring Recommendations

Alert on anomalous admin-session activity such as plugin or user creation actions originating from pages that render subscriber data.
Monitor file integrity of wp-content/plugins/email-subscription-with-secure-captcha/ for unauthorized modification.
Track Content Security Policy (CSP) violation reports from the WordPress admin and public pages that embed the subscription widget.

How to Mitigate CVE-2025-11994

Immediate Actions Required

Deactivate the Easy Email Subscription plugin until a patched release is installed if your site is running version 1.3 or earlier.
Audit the plugin's subscriber table and remove or sanitize entries containing HTML or scripting content.
Rotate WordPress administrator credentials and invalidate active sessions if XSS indicators are found.

Patch Information

The vendor addressed the issue in WordPress.org changeset 3388578 for the email-subscription-with-secure-captcha plugin. Site operators should update to the version published after this changeset. Additional technical context is available in the Wordfence Vulnerability Report and the upstream files simple-email-subscription.php and subscriber-form.php.

Workarounds

Restrict access to the subscription form behind CAPTCHA enforcement, IP allow-listing, or a reverse proxy rule that filters HTML metacharacters in the name parameter.
Deploy a WAF rule that blocks POST payloads containing <script, onerror=, or javascript: patterns against the subscription endpoint.
Apply a strict Content Security Policy that disallows inline scripts in the WordPress admin to reduce post-injection impact.

bash

# Example WAF rule (ModSecurity) blocking script payloads in the name parameter
SecRule ARGS:name "@rx (?i)(<script|onerror=|onload=|javascript:)" \
    "id:1011994,phase:2,deny,status:403,log,\
     msg:'CVE-2025-11994 - Stored XSS attempt against Easy Email Subscription'"