CVE-2021-40909 in PHP CRUD Tutorial
Summary
by MITRE • 01/24/2022
Cross site scripting (XSS) vulnerability in sourcecodester PHP CRUD without Refresh/Reload using Ajax and DataTables Tutorial v1 by oretnom23, allows remote attackers to execute arbitrary code via the first_name, last_name, and email parameters to /ajax_crud.
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Analysis
by VulDB Data Team • 01/28/2022
This cross site scripting vulnerability exists in the PHP CRUD application tutorial version 1 developed by oretnom23, specifically within the /ajax_crud endpoint that handles user data operations. The flaw stems from insufficient input validation and output sanitization mechanisms that fail to properly handle malicious payloads submitted through the first_name, last_name, and email parameters. The vulnerability occurs in the context of a web application that utilizes Ajax and DataTables for dynamic data handling without requiring page refreshes, making the attack surface particularly concerning for user interaction scenarios.
The technical implementation of this vulnerability demonstrates a classic XSS flaw where user-supplied data flows directly into HTML output without appropriate encoding or sanitization. When attackers submit malicious JavaScript code through any of the three vulnerable parameters, the application stores and displays this content without proper context-aware escaping. This allows the malicious script to execute within the victim's browser context, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The vulnerability operates under CWE-79 which specifically addresses Cross-Site Scripting flaws in web applications, and aligns with ATT&CK technique T1566.001 for initial access through malicious content.
The operational impact of this vulnerability extends beyond simple script execution as it enables attackers to manipulate the application's user interface and data presentation. An attacker could inject malicious scripts that steal cookies, redirect users to phishing sites, or even modify the application's behavior to exfiltrate sensitive information. The Ajax-based architecture of this application means that the vulnerability could be exploited during any data submission or display operation, potentially affecting multiple users who interact with the affected application components. The lack of proper input validation at the server-side level creates a persistent threat vector that remains active until the underlying sanitization mechanisms are properly implemented.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input validation and output encoding mechanisms throughout the application stack. All user-supplied data must be validated against expected formats and sanitized before storage or display, with particular attention to HTML and JavaScript content. The implementation should follow secure coding practices that align with OWASP Top 10 recommendations and the principle of least privilege for data handling. Additionally, Content Security Policy headers should be implemented to provide an additional layer of protection against XSS attacks, while regular security testing including dynamic application security testing and manual penetration testing should be conducted to identify similar vulnerabilities. The fix must ensure that all parameters including first_name, last_name, and email are properly escaped when rendered in HTML contexts, and that the application implements proper sanitization routines that prevent malicious payloads from being executed in the browser.