Executive Summary

CVE-2026-6159 is a Stored Cross-Site Scripting (XSS) vulnerability found in Simple Chatbox PHP version 1.0. It occurs in the message submission functionality at the endpoint /SimpleChatbox_PHP/chatbox/insert.php, specifically in the msg parameter received via an HTTP GET request.

The vulnerability arises because the application accepts user input through the msg parameter without validation or sanitization, stores it directly, and later renders it in the chat interface without output encoding. This allows attackers to inject malicious HTML or JavaScript code that is stored on the server and executed in the browsers of users viewing the chat.

For example, an attacker can send a crafted GET request like /SimpleChatbox_PHP/chatbox/insert.php?msg=Hello<script>alert(1)</script>, which results in the execution of the injected script when the chat interface is loaded.

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Impact Analysis

This vulnerability allows attackers to execute arbitrary JavaScript code in the browsers of users who view the chat messages. The impacts include:

• Stealing session cookies, which can lead to hijacking user sessions.
• Performing actions on behalf of users without their consent.
• Injecting malicious or phishing content that can deceive users.
• Potentially compromising the security and privacy of all users interacting with the chat interface.

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Detection Guidance

This vulnerability can be detected by sending crafted HTTP GET requests to the vulnerable endpoint and observing if injected scripts execute in the chat interface.

• Send a GET request to /SimpleChatbox_PHP/chatbox/insert.php with a payload in the msg parameter, for example: /SimpleChatbox_PHP/chatbox/insert.php?msg=Hello<script>alert(1)</script>
• If the injected script executes (e.g., an alert box appears), the system is vulnerable to stored XSS.
• Use tools like curl or wget to automate the test, for example: curl "http://target/SimpleChatbox_PHP/chatbox/insert.php?msg=<script>alert(1)</script>"
• Monitor the chat interface in a browser to see if the injected script runs when loading messages.

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Mitigation Strategies

Immediate mitigation steps include sanitizing and encoding user input to prevent script injection and execution.

• Apply output encoding on the msg parameter before rendering, for example using htmlspecialchars($msg, ENT_QUOTES, 'UTF-8') in PHP.
• Sanitize user input before storing it to remove or neutralize malicious code.
• Implement a Content Security Policy (CSP) header such as Content-Security-Policy: default-src 'self' to restrict script execution sources.
• Avoid directly echoing user input without validation or encoding.

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Compliance Impact

The vulnerability is a Stored Cross-Site Scripting (XSS) issue that allows attackers to execute arbitrary JavaScript in the browsers of users viewing the chat. This can lead to session hijacking, theft of cookies, and unauthorized actions on behalf of users.

While the provided information does not explicitly mention compliance with standards like GDPR or HIPAA, such vulnerabilities can impact compliance because they may lead to unauthorized access or disclosure of personal data, which these regulations aim to protect.

Therefore, failure to remediate this vulnerability could result in violations of data protection requirements under regulations like GDPR and HIPAA, especially if personal or sensitive information is exposed or compromised through the XSS attack.

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