CVE-2025-57940: Append Extensions on Pages XSS Vulnerability

CVE-2025-57940 Overview

CVE-2025-57940 is a stored Cross-Site Scripting (XSS) vulnerability in the Suresh Kumar Mukhiya Append extensions on Pages WordPress plugin. The flaw affects all versions from initial release through 1.1.2. It stems from improper neutralization of user-supplied input during web page generation, mapped to [CWE-79]. An authenticated attacker with high privileges can inject persistent JavaScript payloads that execute in the browsers of users who view affected pages. Successful exploitation crosses a security scope boundary, extending impact beyond the vulnerable component itself.

Critical Impact
Authenticated attackers can inject persistent JavaScript into WordPress pages, enabling session theft, administrative account takeover, and content manipulation against site visitors and administrators.

Affected Products

Suresh Kumar Mukhiya Append extensions on Pages plugin for WordPress
All versions up to and including 1.1.2
WordPress sites with the append-extensions-on-pages plugin installed and active

Discovery Timeline

2025-09-22 - CVE-2025-57940 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-57940

Vulnerability Analysis

The vulnerability is a stored XSS in the Append extensions on Pages plugin. The plugin fails to sanitize or encode user input before rendering it as part of the generated web page HTML. When an attacker submits input containing script content through an affected plugin field, the payload is persisted in the WordPress database. The payload later executes in the browser context of any user who loads a page rendered by the plugin. Because the injected script runs under the origin of the WordPress site, it inherits access to authentication cookies, session state, and the WordPress REST API surface available to the viewing user.

Root Cause

The root cause is missing output encoding and input sanitization in the plugin's page-rendering logic. Input received from privileged users is written back into HTML output without passing through WordPress escaping functions such as esc_html(), esc_attr(), or wp_kses_post(). This allows arbitrary HTML and JavaScript to survive round-tripping through the database and execute on render.

Attack Vector

Exploitation requires an authenticated user with high privileges and one additional user interaction to trigger the payload. The attacker stores a script payload through the plugin's page-append functionality. When another user, typically an administrator or site visitor, browses to a page that includes the injected content, the browser executes the payload. The scope change indicates that the injected script can affect resources beyond the plugin, including the surrounding WordPress admin session. Refer to the Patchstack Vulnerability Report for the technical write-up.

No verified proof-of-concept code is publicly available for this issue. The vulnerability manifests wherever the plugin renders stored input without escaping.

Detection Methods for CVE-2025-57940

Indicators of Compromise

Unexpected <script>, <iframe>, onerror, or onload attributes stored in WordPress wp_posts or plugin-specific database tables
Outbound browser requests from authenticated admin sessions to unfamiliar domains shortly after loading affected pages
New WordPress administrator accounts or modified user roles created without an audit trail
Modified plugin, theme, or wp-config.php files following administrator page views

Detection Strategies

Scan the WordPress database for HTML event handlers and script tags in fields written by the append-extensions-on-pages plugin
Inventory installed WordPress plugins and flag any instance of append-extensions-on-pages at version 1.1.2 or earlier
Deploy a web application firewall rule set that inspects POST requests to plugin endpoints for script payloads and HTML entities
Review web server access logs for privileged user submissions containing encoded angle brackets or JavaScript URIs

Monitoring Recommendations

Alert on creation or privilege escalation of WordPress users following admin visits to plugin-rendered pages
Monitor Content Security Policy (CSP) violation reports for inline script executions on pages using the plugin
Track file integrity of the WordPress installation and enable audit logging for plugin configuration changes

How to Mitigate CVE-2025-57940

Immediate Actions Required

Deactivate and remove the append-extensions-on-pages plugin until a patched version is confirmed available
Audit all pages rendered by the plugin and remove stored HTML that contains script tags or event handlers
Rotate WordPress administrator passwords and invalidate active sessions if exploitation is suspected
Restrict the assignment of high-privilege WordPress roles to only trusted users

Patch Information

No fixed version is listed in the NVD entry at the time of publication. The advisory indicates the issue affects versions up to and including 1.1.2. Monitor the Patchstack Vulnerability Report and the WordPress plugin repository for a vendor-supplied fix.

Workarounds

Uninstall the plugin and replace its functionality with a maintained alternative that escapes output
Enforce a strict Content Security Policy that blocks inline scripts on WordPress-rendered pages
Place a web application firewall in front of wp-admin to filter script payloads in plugin form submissions
Restrict the WordPress unfiltered_html capability so that fewer roles can submit raw HTML

bash

# Example: disable the vulnerable plugin from WP-CLI
wp plugin deactivate append-extensions-on-pages
wp plugin delete append-extensions-on-pages

# Example: enforce a restrictive CSP via .htaccess
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'"