CVE-2021-20112 in TCExam
Summary
by MITRE • 07/30/2021
A stored cross-site scripting vulnerability exists in TCExam
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Analysis
by VulDB Data Team • 08/05/2021
The stored cross-site scripting vulnerability in TCExam represents a critical security flaw that allows attackers to inject malicious scripts into the application's database, which are then executed when other users view the affected content. This vulnerability specifically affects the TCExam learning management system, which is widely used for online testing and examination administration in educational institutions and corporate training environments. The flaw enables persistent XSS attacks where malicious code can be stored in the application's backend and executed in the context of other users' browsers, potentially leading to session hijacking, credential theft, or further exploitation of the affected systems.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the TCExam application's data handling mechanisms. When users submit data through various application interfaces, the system fails to properly sanitize or escape special characters that could be interpreted as HTML or JavaScript code. This weakness allows attackers to inject malicious payloads that are subsequently stored in the database and rendered when other users access the affected content. The vulnerability is classified as stored XSS because the malicious script is permanently stored on the server rather than being reflected in a single request, making it particularly dangerous as it can affect multiple users over time.
The operational impact of this vulnerability extends beyond simple script execution, as it creates a persistent threat vector that can be exploited to compromise user sessions and potentially gain unauthorized access to sensitive examination data. Attackers could manipulate exam results, access confidential student information, or use the compromised sessions to perform administrative actions within the TCExam environment. The attack surface is particularly concerning in educational settings where TCExam is used for high-stakes testing, as it could lead to academic integrity violations, data breaches, and potential exposure of proprietary exam content. Additionally, the vulnerability may enable attackers to establish persistent backdoors or use the compromised system as a staging area for further attacks against the broader network infrastructure.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input validation and output encoding mechanisms throughout the TCExam application. Security patches should include proper sanitization of all user inputs before storage, implementation of Content Security Policy headers, and regular security audits of data handling processes. Organizations should also consider implementing web application firewalls to detect and block suspicious payloads, conduct regular penetration testing to identify similar vulnerabilities, and ensure that all users are running the latest patched versions of the software. This vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws, and represents a common attack pattern categorized under the ATT&CK framework as T1566.001, focusing on the exploitation of web application vulnerabilities for initial access and privilege escalation within target environments.