Cross-Site Scripting in Class and Exam Timetabling System

Executive Summary

CVE-2026-15595 is a Cross-Site Scripting (XSS) vulnerability found in the SourceCodester Class and Exam Timetabling System 1.0. The issue occurs in the '/forsubject.php' file, where the 'subject' parameter is not properly validated or encoded.

An attacker can exploit this flaw by injecting malicious script code into the 'subject' parameter. When a victim accesses the affected page, the injected script executes in their browser without proper sanitization. This can lead to unauthorized actions, such as stealing sensitive data (e.g., cookies or session tokens), defacing web pages, or redirecting users to malicious sites.

The vulnerability can be triggered remotely and does not require authentication or authorization. An example payload provided is '<script>prompt(/xss/);</script>'.

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Detection Guidance

To detect the CVE-2026-15595 vulnerability on your network or system, you can check for the presence of the vulnerable '/forsubject.php' file in the SourceCodester Class and Exam Timetabling System 1.0. The vulnerability involves improper input validation of the 'subject' parameter, which can be tested for XSS exploitation.

• Use a web vulnerability scanner like OWASP ZAP or Burp Suite to scan for XSS vulnerabilities in the application. Focus on the '/forsubject.php' endpoint.
• Manually test the 'subject' parameter by injecting a simple XSS payload, such as '<script>prompt(/xss/);</script>', and observe if the script executes in the browser. Example command for testing via curl: curl -X GET 'http://<target>/forsubject.php?subject=<script>prompt(/xss/);</script>'.
• Check the application's source code for the '/forsubject.php' file and review how the 'subject' parameter is handled. Look for missing input validation or output encoding.
• Monitor network traffic for unusual requests to '/forsubject.php' with suspicious parameters, which may indicate exploitation attempts.

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Impact Analysis

If you are a user or administrator of the SourceCodester Class and Exam Timetabling System 1.0, this vulnerability could have several impacts:

• Theft of sensitive information: Attackers could steal cookies, session tokens, or other sensitive data stored in the browser.
• Unauthorized actions: Malicious scripts could perform actions on your behalf, such as changing settings, submitting forms, or accessing restricted areas.
• Web page defacement: Attackers could alter the appearance or content of the web page to mislead or deceive users.
• Redirection to malicious sites: Users could be redirected to phishing or malware-hosting websites without their knowledge.

Since the vulnerability can be exploited without requiring login or authorization, any user interacting with the affected system is at risk.

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Compliance Impact

This vulnerability could impact compliance with several standards and regulations, depending on the context in which the affected system is used:

• GDPR (General Data Protection Regulation): If the system processes or stores personal data of EU citizens, an XSS vulnerability could lead to unauthorized access or theft of this data. This may result in a violation of GDPR's data protection principles, particularly the requirements for confidentiality and integrity of personal data (Article 5). Additionally, if a breach occurs, it may trigger the obligation to report the incident to authorities and affected individuals (Article 33 and 34).
• HIPAA (Health Insurance Portability and Accountability Act): If the system is used in a healthcare environment to manage or store protected health information (PHI), an XSS vulnerability could expose this sensitive data to unauthorized parties. This would violate HIPAA's Security Rule, which requires safeguards to protect the confidentiality, integrity, and availability of PHI.
• Other standards: The vulnerability may also affect compliance with frameworks like ISO 27001, which requires organizations to implement controls to manage information security risks, including those related to web applications. Similarly, PCI DSS (Payment Card Industry Data Security Standard) could be impacted if the system handles payment card data, as XSS vulnerabilities can lead to the theft of such information.

Failure to address this vulnerability could result in regulatory penalties, legal liabilities, and reputational damage for organizations subject to these standards.

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Mitigation Strategies

To mitigate CVE-2026-15595, follow these immediate steps to reduce the risk of exploitation:

• Apply proper output encoding to the 'subject' parameter in '/forsubject.php' to prevent malicious script execution. Use functions like htmlspecialchars() in PHP to sanitize output.
• Implement input validation for the 'subject' parameter to ensure only expected data is accepted. Use allowlists for permitted characters or patterns.
• Deploy a Content Security Policy (CSP) header to restrict the sources of executable scripts and mitigate the impact of any potential XSS attacks.
• Set the 'Secure' and 'HttpOnly' flags for cookies to prevent theft via XSS attacks.
• Temporarily restrict access to the '/forsubject.php' file if immediate patching is not possible, or apply a web application firewall (WAF) rule to block malicious payloads.
• Conduct a security audit of the application to identify and fix similar vulnerabilities in other parts of the system.

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