CVE-2021-26304 in Daily Expense Tracker System
Summary
by MITRE • 01/29/2021
PHPGurukul Daily Expense Tracker System 1.0 is vulnerable to stored XSS via the add-expense.php Item parameter.
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Analysis
by VulDB Data Team • 02/21/2021
The PHPGurukul Daily Expense Tracker System version 1.0 contains a critical stored cross-site scripting vulnerability that affects the add-expense.php web page. This vulnerability specifically targets the Item parameter which is used to capture expense item descriptions entered by users. When an attacker submits malicious script code through this parameter, the system fails to properly sanitize or escape the input before storing it in the database. The vulnerability stems from inadequate input validation and output encoding mechanisms within the application's data handling processes, creating a persistent security flaw that can affect all users who view the affected expense records.
This stored XSS vulnerability operates through a classic attack vector where malicious code is first submitted by an attacker and then stored on the server side. When other users navigate to pages displaying the compromised expense data, their browsers execute the malicious scripts within the context of the vulnerable application. The attack leverages the trust relationship between the user's browser and the web application, allowing threat actors to potentially steal session cookies, perform unauthorized actions on behalf of users, or redirect victims to malicious websites. The vulnerability is particularly concerning because it affects the core functionality of the expense tracking system and can persist even after the initial attack occurs.
The operational impact of this vulnerability extends beyond simple data corruption or display issues. Attackers can exploit this weakness to hijack user sessions, execute arbitrary JavaScript code, and potentially escalate privileges within the application's security boundaries. The stored nature of the vulnerability means that the malicious payload remains active until manually removed from the database, providing attackers with persistent access to the system. This vulnerability directly relates to CWE-79 which defines cross-site scripting flaws as weaknesses that allow attackers to inject malicious scripts into web applications viewed by other users. The attack surface is significantly broadened as any user who can submit expense data and subsequently view it becomes a potential victim of this stored XSS attack.
Organizations using this vulnerable system should implement immediate mitigations including comprehensive input sanitization, output encoding, and proper content security policies. The recommended approach involves validating all user inputs against strict whitelists, implementing proper HTML escaping for all dynamic content, and deploying web application firewalls to detect and block malicious payloads. Additionally, regular security testing and code reviews should be conducted to identify similar vulnerabilities in other application components. The implementation of CSP headers and proper session management can significantly reduce the attack surface and limit the potential damage from successful exploitation attempts. This vulnerability aligns with several ATT&CK techniques including T1059 for command and scripting interpreter and T1531 for credential access through session hijacking, demonstrating the comprehensive threat landscape that stored XSS vulnerabilities can create for organizations.