CVE-2020-5748 in TCExam
Summary
by MITRE
Insufficient output sanitization in TCExam 14.2.2 allows a remote, unauthenticated attacker to conduct persistent cross-site scripting (XSS) attacks via the self-registration feature.
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Analysis
by VulDB Data Team • 05/08/2020
The vulnerability identified as CVE-2020-5748 resides within TCExam version 14.2.2, a widely used web-based examination system that facilitates online testing and assessment management. This particular flaw represents a critical security weakness in the application's input validation mechanisms, specifically affecting the self-registration functionality that allows users to create accounts without administrative intervention. The vulnerability manifests as insufficient output sanitization, meaning that the application fails to properly filter or escape user-supplied data before rendering it in web responses, creating an avenue for malicious actors to inject persistent cross-site scripting payloads.
The technical exploitation of this vulnerability occurs through the self-registration feature, which serves as the primary attack vector for unauthenticated remote attackers. When users register through this mechanism, their input data is processed and stored within the application's database without adequate sanitization of potentially malicious content. The flaw allows attackers to submit crafted payloads containing javascript code or other malicious scripts that get stored and subsequently executed whenever the affected page is rendered to other users. This persistent nature of the vulnerability means that once a malicious payload is injected, it continues to execute for all users who view the affected content, making it particularly dangerous for web applications that serve multiple users simultaneously.
The operational impact of CVE-2020-5748 extends beyond simple data corruption or display issues, as it provides attackers with the capability to execute arbitrary code within the context of affected users' browsers. This vulnerability directly aligns with CWE-79, which describes cross-site scripting flaws where applications fail to properly sanitize user input before rendering it in web pages. The persistent nature of the XSS attack means that attackers can establish long-term footholds within the application environment, potentially enabling them to steal session cookies, perform unauthorized actions on behalf of users, or redirect victims to malicious websites. Given that TCExam systems are typically used for educational and professional testing environments, the compromise of such systems could lead to unauthorized access to sensitive examination data, impersonation of legitimate users, and potential disruption of assessment processes.
Security professionals should consider this vulnerability in the context of the ATT&CK framework, particularly under the T1059.007 technique for scripting languages and T1531 for credential access through compromised accounts. The vulnerability's exploitation pathway creates opportunities for attackers to establish persistent access and escalate privileges within the examination environment. Mitigation strategies should focus on implementing comprehensive input validation and output encoding mechanisms throughout the application, particularly around user input fields in registration forms. Organizations should immediately apply the vendor-provided patches or updates that address this specific sanitization issue, while also implementing additional security measures such as content security policies and regular security audits of user input handling mechanisms. The vulnerability underscores the critical importance of proper input sanitization and output encoding practices, as recommended by OWASP Top Ten and other industry security standards, to prevent such persistent cross-site scripting vulnerabilities from compromising web application security.