CVE-2025-53294: Smart Agenda Stored XSS Vulnerability

CVE-2025-53294 Overview

CVE-2025-53294 is a stored Cross-Site Scripting (XSS) vulnerability in the Smart Agenda smart-agenda-prise-de-rendez-vous-en-ligne WordPress plugin. The flaw affects all versions up to and including 4.9. The issue stems from improper neutralization of user-supplied input during web page generation, categorized under [CWE-79]. Authenticated attackers with low privileges can inject malicious scripts that persist in the application and execute in the browsers of other users who view the affected pages.

Critical Impact
Authenticated attackers can inject persistent JavaScript payloads that execute in victims' browsers, enabling session hijacking, credential theft, and administrative account takeover through cross-site scripting in a scope-changing context.

Affected Products

Smart Agenda smart-agenda-prise-de-rendez-vous-en-ligne WordPress plugin
All versions from n/a through 4.9
WordPress sites with the Smart Agenda appointment booking plugin installed

Discovery Timeline

2025-06-27 - CVE CVE-2025-53294 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-53294

Vulnerability Analysis

The Smart Agenda plugin fails to properly sanitize and encode user-supplied input before rendering it in web pages. This stored XSS variant persists the malicious payload server-side, causing execution each time a victim loads the affected page. The vulnerability requires low-level authentication and user interaction, but the scope changes to impact other users beyond the attacker's own session.

The attack surface centers on input fields exposed by the appointment booking plugin. When administrators or other users view the injected content in the WordPress admin dashboard, the payload executes in their authenticated session context.

Root Cause

The root cause is improper neutralization of input during web page generation [CWE-79]. The plugin accepts user input and stores it without applying output encoding or context-aware sanitization when rendering the data back to HTML. WordPress functions such as esc_html(), esc_attr(), or wp_kses() are either missing or misapplied in the affected code paths.

Attack Vector

An authenticated attacker submits a crafted payload through the plugin's input fields. The malicious content is stored in the WordPress database. When another user, typically an administrator, loads the page containing the stored payload, the script executes in their browser. This enables the attacker to hijack sessions, exfiltrate cookies, perform actions on behalf of the victim, or pivot to full site compromise.

Refer to the Patchstack XSS Vulnerability Advisory for further technical details.

Detection Methods for CVE-2025-53294

Indicators of Compromise

Unexpected <script>, onerror, onload, or javascript: strings stored in Smart Agenda plugin database tables
Outbound HTTP requests from administrator browsers to unfamiliar domains after loading plugin pages
Anomalous WordPress admin session activity, such as new administrator accounts or modified user roles
HTML-encoded or Base64-encoded payloads in appointment booking fields

Detection Strategies

Audit database rows written by the Smart Agenda plugin for HTML tags or JavaScript event handlers
Deploy a Web Application Firewall (WAF) rule to flag XSS patterns targeting the plugin's endpoints
Enable WordPress activity logging to correlate low-privilege user input submissions with subsequent administrator page views
Monitor Content Security Policy (CSP) violation reports from browsers loading the admin dashboard

Monitoring Recommendations

Track WordPress plugin version inventory to identify installations at or below Smart Agenda 4.9
Alert on newly created administrator accounts or unexpected role changes following plugin usage
Log and review all POST requests to Smart Agenda plugin endpoints, correlating source IPs with authenticated user accounts
Ingest WordPress and web server logs into a centralized data lake for retrospective XSS pattern hunting

How to Mitigate CVE-2025-53294

Immediate Actions Required

Identify all WordPress sites running the Smart Agenda plugin at version 4.9 or earlier
Restrict access to plugin functionality to trusted, authenticated users only
Enforce a strict Content Security Policy that disables inline script execution on WordPress admin pages
Audit existing plugin data for previously injected payloads and remove malicious content

Patch Information

At the time of the NVD entry, the advisory indicates the vulnerability affects Smart Agenda versions up to and including 4.9. Site administrators should consult the Patchstack XSS Vulnerability Advisory and the plugin vendor's release notes for the fixed version and upgrade instructions.

Workarounds

Deactivate and remove the Smart Agenda plugin until a patched version is installed
Deploy a WAF ruleset that blocks XSS payloads targeting WordPress plugin endpoints
Enforce least-privilege on WordPress user roles to limit which accounts can submit plugin input
Apply a restrictive Content Security Policy header to reduce inline script execution risk

bash

# Example nginx CSP header to mitigate XSS execution in WordPress admin
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'self';" always;