CVE-2025-11496 Exploit & Vulnerability Analysis

1. Vulnerability Background

What is this vulnerability?

• CVE-2025-11496 is a stored cross-site scripting (XSS) vulnerability in the Five Star Restaurant Reservations – WordPress Booking Plugin.
• The issue is rooted in insufficient output escaping of booking data, including the rtb-name parameter and related user-supplied fields.
• User input is persisted by the plugin and later rendered in HTML contexts, allowing arbitrary script injection.

Why is it critical/important?

• Stored XSS is a high-risk vulnerability because the attacker-controlled payload is saved on the server and executed whenever a victim loads the affected page.
• In this case, payloads can reach site administrators or users via booking notification pages, backend booking listings, or rendered notification templates.
• Successful exploitation can lead to session theft, account takeover, arbitrary actions as authenticated users, or further compromise of the WordPress installation.

What systems/versions are affected?

• All versions of the Five Star Restaurant Reservations – WordPress Booking Plugin up to and including 2.7.5 are affected.
• The vulnerability is present in the plugin’s booking notification and admin display code.

2. Technical Details

Root cause analysis

• The plugin stored user-controlled booking data and later injected it directly into HTML without applying context-appropriate escaping.
• In includes/Notification.class.php, template replacement values were built using raw properties from the booking object.
• In includes/Notifications.class.php, booking fields were echoed directly into table cells.
• In includes/template-functions.php, label text and attribute values were output without proper escaping.

Attack vector and exploitation conditions

• An unauthenticated attacker submits a booking containing malicious content in fields such as:
  • name (rtb-name)
  • email
  • phone
  • message
• Because the booking data is stored and later displayed, the payload persists.
• When an administrator or other user loads the affected UI or notification page, the browser interprets the injected payload as executable HTML/JavaScript.

Security implications

• Stored XSS on administrative interfaces is particularly dangerous.
• The vulnerability can be abused to:
  • execute JavaScript in the context of authenticated users
  • steal cookies or authorization tokens
  • perform actions via CSRF using the victim’s session
  • pivot to further attacks against the WordPress site

3. Patch Analysis

What code changes were made?

• includes/Notification.class.php
  • Old: raw booking data inserted into notification template tags
  • Fixed: esc_html() applied to $this->booking->email, $this->booking->name, $this->booking->phone, and $this->booking->message
• includes/Notifications.class.php
  • Old: raw $booking_object->party, $booking_object->name, $booking_object->email, $booking_object->phone echoed directly
  • Fixed: esc_html() applied to each output
• includes/template-functions.php
  • Old: $title output directly in label, and type, name, id attributes rendered without attribute escaping
  • Fixed: esc_html($title) in label; esc_attr() applied to $type, $slug, and $value where they are used in the input element

How do these changes fix the vulnerability?

• The patch moves escaping to the output layer, ensuring user-supplied data is rendered as plain text rather than interpreted as HTML/JS.
• esc_html() encodes HTML special characters in text content.
• esc_attr() encodes special characters inside HTML attributes, preventing injections via type, name, and id.

Security improvements introduced

• Raw user input no longer reaches HTML rendering contexts unescaped.
• Multiple XSS sinks are protected:
  • notification template substitution
  • admin booking list display
  • form field labels and attribute values
• The fix adheres to WordPress best practice: escape at the point of output using the correct escaping function for the context.

4. Proof of Concept (PoC) Guide

Prerequisites for exploitation

• Vulnerable plugin version installed (<= 2.7.5)
• Access to the booking submission form
• Ability to submit arbitrary text into one or more booking fields

Step-by-step exploitation approach

1. Submit a booking through the plugin’s reservation form.
2. In a vulnerable field such as rtb-name, enter a payload like: <script>alert('xss')</script>
3. Complete and submit the booking.
4. Access the page or notification where the booking is rendered:
   • booking notification template
   • admin bookings list
   • rendered notification email HTML
5. Observe whether the payload executes in the browser.

Expected behavior vs exploited behavior

• Expected behavior in patched code:
  • injected payload is displayed as escaped text, e.g. <script>alert('xss')</script>
  • no script execution
• Exploited behavior in vulnerable versions:
  • browser executes the injected script
  • alert dialog or other malicious action occurs

How to verify the vulnerability exists

• Confirm plugin version is 2.7.5 or earlier.
• Locate the booking display page and inspect source for raw booking values.
• Submit a test payload and verify execution on a page that renders booking data.
• Review affected source code for missing esc_html() / esc_attr() around user-controlled output.

5. Recommendations

Mitigation strategies

• Upgrade the plugin to the patched version that includes the escaping fixes.
• If patching is not immediately possible, remove or restrict access to the booking form and admin booking pages.
• Implement a Content Security Policy (CSP) to reduce the impact of reflected/stored XSS.

Detection methods

• Audit plugin source files for output escaping in user-controlled contexts.
• Scan for uses of echo or template substitution with booking object properties without esc_html() or esc_attr().
• Use WordPress-focused scanning tools and static code analysis to detect missing escaping.
• Monitor the plugin version installed and apply updates promptly.

Best practices to prevent similar issues

• Always escape user-supplied data at the point of output, using context-appropriate functions.
• Use esc_html() for HTML text content and esc_attr() for attribute values.
• Avoid relying solely on input sanitization; output escaping is the primary defense against XSS.
• Treat any stored user input as untrusted, especially in admin-facing interfaces.
• Review and test template rendering paths for XSS vulnerabilities during development and code review.