CVE-2026-3302: Doctor Appointment System XSS Vulnerability

CVE-2026-3302 Overview

A Cross-Site Scripting (XSS) vulnerability has been identified in SourceCodester Doctor Appointment System version 1.0. The vulnerability exists in the /register.php file within the Sign Up Page component. An attacker can exploit this flaw by manipulating the Email argument to inject malicious scripts, which can then be executed in the context of a victim's browser session. The attack can be launched remotely without authentication, and a proof-of-concept exploit has been made publicly available.

Critical Impact
Remote attackers can inject arbitrary scripts into the application, potentially leading to session hijacking, credential theft, or malicious actions performed on behalf of authenticated users.

Affected Products

SourceCodester Doctor Appointment System 1.0
remyandrade doctor_appointment_system

Discovery Timeline

2026-02-27 - CVE CVE-2026-3302 published to NVD
2026-02-27 - Last updated in NVD database

Technical Details for CVE-2026-3302

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The vulnerable component is the registration functionality located in /register.php, specifically within the Sign Up Page. The application fails to properly sanitize user-supplied input in the Email field before rendering it back to users, creating an injection point for malicious scripts.

The vulnerability allows attackers to inject arbitrary JavaScript code that executes in the browser context of users who view the affected page. This can result in theft of session cookies, redirection to malicious sites, defacement of the web application, or phishing attacks against application users.

Root Cause

The root cause is improper input validation and output encoding in the registration form processing logic. The Email parameter is accepted and reflected in the HTML response without adequate sanitization or encoding. This allows attackers to break out of the expected HTML context and inject executable script content.

Attack Vector

The attack is network-based and can be executed remotely. An attacker crafts a malicious payload containing JavaScript code and submits it through the Email field in the registration form. When this data is rendered in the application, the malicious script executes in the victim's browser.

The vulnerability requires user interaction (a victim must visit the page containing the injected payload) but does not require authentication to exploit. A publicly available proof-of-concept demonstrates the exploitation technique, as documented in the GitHub PoC Repository.

Detection Methods for CVE-2026-3302

Indicators of Compromise

Unusual JavaScript code appearing in Email field values in application logs
HTTP requests containing encoded script tags (%3Cscript%3E) or event handlers (onerror, onload) in the Email parameter
Reports of unexpected pop-ups or redirections from users interacting with the registration page

Detection Strategies

Implement Web Application Firewall (WAF) rules to detect XSS payloads in form submissions targeting /register.php
Monitor application logs for Email field entries containing HTML tags or JavaScript event handlers
Deploy browser-based XSS detection mechanisms such as Content Security Policy (CSP) violation reporting

Monitoring Recommendations

Enable detailed logging for all form submissions to the /register.php endpoint
Configure alerts for patterns matching common XSS payloads in user input fields
Review access logs for unusual activity patterns targeting the Sign Up Page

How to Mitigate CVE-2026-3302

Immediate Actions Required

Implement strict input validation on the Email field to allow only valid email address formats
Apply context-appropriate output encoding when displaying user-supplied data in HTML pages
Deploy Content Security Policy (CSP) headers to prevent inline script execution
Consider temporarily disabling the registration functionality until a patch is applied

Patch Information

No official vendor patch is currently available for this vulnerability. The application is distributed through SourceCodester, and users should monitor for updates. Additional vulnerability details are available through VulDB Entry #348053.

Workarounds

Implement server-side input sanitization using established security libraries to strip or encode HTML special characters
Deploy a Web Application Firewall (WAF) with XSS filtering rules in front of the application
Add client-side validation as a defense-in-depth measure (not a primary control)
Consider implementing HTTPOnly and Secure flags on session cookies to limit XSS impact

bash

# Example Apache configuration for Content Security Policy header
# Add to .htaccess or Apache virtual host configuration
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'"