CVE-2025-58018: Mail Subscribe List Stored XSS Vulnerability

CVE-2025-58018 Overview

CVE-2025-58018 is a stored Cross-Site Scripting (XSS) vulnerability in the Richard Leishman Mail Subscribe List plugin for WordPress. The flaw affects all versions of mail-subscribe-list up to and including 2.1.10. The vulnerability results from improper neutralization of user-supplied input during web page generation, categorized as [CWE-79]. Successful exploitation requires low-privileged authenticated access and user interaction, but the resulting script executes in a changed security scope, enabling attackers to impact other users and site components.

Critical Impact
Authenticated attackers can inject persistent JavaScript payloads that execute in the browsers of site visitors and administrators, enabling session theft, administrative action forgery, and pivoting into the WordPress admin interface.

Affected Products

Richard Leishman Mail Subscribe List plugin for WordPress
All versions from initial release through 2.1.10
WordPress sites with the vulnerable plugin activated

Discovery Timeline

2025-09-22 - CVE-2025-58018 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-58018

Vulnerability Analysis

The Mail Subscribe List plugin fails to sanitize input before storing and rendering it within generated web pages. An authenticated user with low privileges can submit crafted input containing HTML or JavaScript. The plugin persists this input and later returns it to other users without applying output encoding or contextual escaping.

Because the payload is stored server-side, every subsequent page render delivers the malicious script to viewers. The CVSS vector indicates a scope change, meaning the injected script executes outside the vulnerable component's original security boundary. This typically manifests as script execution in the WordPress administrator context when staff review subscriber data.

Root Cause

The root cause is missing input validation and output escaping on subscriber-related fields handled by the plugin. WordPress provides helpers such as sanitize_text_field(), wp_kses(), and esc_html() for these purposes. The plugin does not apply these functions consistently to fields that are later rendered in browser contexts, resulting in the [CWE-79] condition.

Attack Vector

Exploitation occurs over the network through standard HTTP requests. An attacker authenticates to the WordPress site with a low-privileged account, submits a subscription or plugin-managed form containing a JavaScript payload, and waits for an administrator or another user to view the affected page. When the victim loads the page, the browser parses and executes the stored script under the site's origin. See the Patchstack XSS Vulnerability Report for advisory details.

Detection Methods for CVE-2025-58018

Indicators of Compromise

Subscriber records or plugin database entries containing <script>, onerror=, onload=, or javascript: strings
Unexpected outbound requests from administrator browsers to attacker-controlled domains after loading plugin admin pages
New administrative WordPress accounts or modified user roles created shortly after admin sessions with the plugin
HTTP POST requests to plugin subscription endpoints containing encoded HTML entities or script tags

Detection Strategies

Query the WordPress database for plugin-managed tables and search stored fields for HTML tags or event handler attributes
Enable a Content Security Policy (CSP) in report-only mode to surface inline script execution originating from plugin-rendered pages
Review web server logs for POST requests to mail-subscribe-list endpoints containing suspicious characters such as <, >, or URL-encoded equivalents
Correlate authentication events for low-privileged accounts with subsequent administrator page loads that trigger script execution alerts

Monitoring Recommendations

Ingest WordPress access logs and PHP error logs into a centralized analytics platform for continuous review
Monitor for anomalous admin session activity, including unexpected AJAX calls or configuration changes following plugin page visits
Alert on modifications to WordPress user tables, particularly role escalations to administrator
Track plugin version inventories across managed WordPress deployments to detect vulnerable installations

How to Mitigate CVE-2025-58018

Immediate Actions Required

Identify all WordPress sites running the Mail Subscribe List plugin and confirm the installed version
Deactivate the plugin on any site running version 2.1.10 or earlier until a patched release is confirmed
Rotate WordPress administrator credentials and invalidate active sessions if exploitation is suspected
Audit subscriber data and plugin-managed tables for injected script content and remove malicious entries

Patch Information

At publication time, the Patchstack advisory lists version 2.1.10 as the last affected release. Administrators should monitor the plugin's WordPress.org page for a fixed release and apply it immediately once available. Until a patch is published, deactivate the plugin or apply the workarounds below.

Workarounds

Deactivate and remove the Mail Subscribe List plugin from affected WordPress installations
Restrict subscription form access using a Web Application Firewall (WAF) rule that blocks HTML tags in relevant parameters
Deploy a strict Content Security Policy that disallows inline scripts on WordPress admin pages
Limit low-privileged account creation and require email verification to reduce the pool of potential attackers

bash

# Example WordPress WP-CLI commands to deactivate the vulnerable plugin
wp plugin list --name=mail-subscribe-list --fields=name,status,version
wp plugin deactivate mail-subscribe-list
wp plugin delete mail-subscribe-list