CVE-2018-18694 in Monstra
Summary
by MITRE
admin/index.php?id=filesmanager in Monstra CMS 3.0.4 allows remote authenticated administrators to trigger stored XSS via JavaScript content in a file whose name lacks an extension. Such a file is interpreted as text/html in certain cases.
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Analysis
by VulDB Data Team • 06/03/2023
The vulnerability CVE-2018-18694 affects Monstra CMS version 3.0.4 and represents a stored cross-site scripting flaw within the administrative interface. This issue specifically resides in the file manager component at admin/index.php?id=filesmanager where authenticated administrators can upload files without proper validation of file extensions. The flaw arises when a malicious user uploads a file that lacks a file extension but contains javascript content, which the system subsequently interprets as text/html in certain contexts. This misclassification creates an opportunity for persistent XSS attacks that can affect other users who access the file manager interface.
The technical implementation of this vulnerability stems from inadequate input validation and improper content type handling within the file upload and rendering processes. When files are uploaded without extensions, the system fails to properly sanitize or validate their content, allowing malicious javascript payloads to be stored on the server. The vulnerability is particularly dangerous because it leverages the administrative privilege of authenticated users to establish persistent XSS vectors that can execute in the context of other administrators or users who view the affected files. This stored XSS condition means that the malicious code remains active until manually removed from the system, making it a long-term security risk.
The operational impact of this vulnerability extends beyond simple XSS execution as it provides attackers with the ability to hijack administrative sessions, steal sensitive data, modify content, or perform unauthorized actions within the CMS. The attack requires only an authenticated administrator account, which significantly reduces the attack surface compared to vulnerabilities requiring additional privileges. This makes the vulnerability particularly concerning for organizations where administrative access is granted to multiple users, as a single compromised administrator account could lead to widespread compromise. The stored nature of the vulnerability means that even after the initial upload, the malicious payload continues to execute whenever the affected files are accessed, creating persistent threat vectors that are difficult to detect and remediate.
Organizations should immediately implement mitigations including restricting file upload capabilities, implementing strict file extension validation, and ensuring proper content type checking for all uploaded files. The vulnerability aligns with CWE-79 which addresses cross-site scripting flaws, and follows ATT&CK technique T1059.007 for command and scripting interpreter. Additional protective measures include implementing web application firewalls to detect and block suspicious file upload patterns, conducting regular security audits of file management components, and ensuring that all administrative interfaces properly sanitize and validate file content. System administrators should also consider implementing principle of least privilege controls to limit the scope of potential damage from compromised administrative accounts. The vulnerability demonstrates the critical importance of proper input validation and content type handling in web applications, particularly within administrative interfaces where elevated privileges can amplify the impact of security flaws.