CVE-2020-5749 in TCExam
Summary
by MITRE
Insufficient output sanitization in TCExam 14.2.2 allows a remote, authenticated attacker to conduct persistent cross-site scripting (XSS) attacks by creating a crafted group.
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Analysis
by VulDB Data Team • 05/08/2020
The vulnerability identified as CVE-2020-5749 resides within TCExam version 14.2.2, a web-based examination management system widely deployed in educational institutions for conducting online assessments. This security flaw represents a critical insufficient output sanitization issue that enables authenticated attackers to execute persistent cross-site scripting attacks through the manipulation of group creation functionality. The vulnerability specifically affects the application's handling of user input within group-related operations, where inadequate validation and sanitization of output data creates exploitable entry points for malicious code injection. Attackers leveraging this vulnerability can craft specially designed group names or descriptions that contain malicious script payloads, which then persist within the application's database and execute whenever the affected group information is rendered to other users.
The technical implementation of this vulnerability stems from the application's failure to properly sanitize user-supplied data before rendering it within web pages. When an authenticated user creates or modifies a group within TCExam, the system accepts input without adequate filtering or encoding of potentially malicious content. This weakness allows attackers to inject javascript code or other malicious payloads that are subsequently stored in the database and executed in the context of other users' browsers when they view the compromised group information. The persistent nature of this vulnerability means that the malicious scripts remain active until manually removed from the application's data store, creating a long-term threat vector for all users who encounter the compromised content. This issue aligns with CWE-79, which specifically addresses cross-site scripting vulnerabilities arising from insufficient output encoding and sanitization of user-controllable data.
The operational impact of CVE-2020-5749 extends beyond simple data theft or defacement, as it provides attackers with persistent access to user sessions and potentially sensitive examination data. An attacker could exploit this vulnerability to steal session cookies, redirect users to malicious domains, or inject additional malicious code that could compromise entire user accounts and examination environments. The authenticated nature of the attack means that attackers need only gain access to a legitimate user account to exploit this vulnerability, making it particularly dangerous in environments where multiple users interact with the examination system. This vulnerability can also be leveraged to escalate privileges within the application, potentially allowing attackers to access administrative functions or examine confidential test materials and student performance data. Organizations relying on TCExam for critical assessment operations face significant risks including data integrity compromise, unauthorized access to examination content, and potential exposure of sensitive student information.
Mitigation strategies for CVE-2020-5749 require immediate implementation of proper input validation and output sanitization measures throughout the application's codebase. Organizations should implement comprehensive data sanitization routines that encode or escape all user-supplied content before storing or rendering it within web pages, following established security practices such as those outlined in the OWASP Top Ten and the ATT&CK framework's defensive techniques. The most effective remediation involves implementing context-specific output encoding for all data rendered to web browsers, particularly when displaying user-generated content such as group names, descriptions, and other editable fields. Additionally, organizations should enforce strict input validation that rejects or sanitizes potentially malicious content including script tags, event handlers, and other XSS attack vectors. Security patches provided by the TCExam vendor should be applied immediately, and organizations should conduct thorough security assessments of their deployment environments to identify any additional related vulnerabilities. Regular security monitoring and user access controls should be implemented to minimize the potential impact of successful exploitation attempts while maintaining proper audit trails of all group creation and modification activities.