CVE-2015-8684 in Exponent
Summary
by MITRE
Exponent CMS before 2.3.7 does not properly restrict the types of files that can be uploaded, which allows remote attackers to conduct cross-site scripting (XSS) attacks and possibly have other unspecified impact as demonstrated by uploading a file with an .html extension, then accessing it via the elFinder functionality.
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Analysis
by VulDB Data Team • 05/13/2026
The vulnerability identified as CVE-2015-8684 affects Exponent CMS versions prior to 2.3.7 and represents a critical security flaw in the content management system's file upload functionality. This issue stems from insufficient validation of file types during the upload process, creating a pathway for malicious actors to exploit the system through cross-site scripting attacks. The vulnerability specifically targets the elFinder file management component within the CMS, which provides users with the ability to upload and manage files through a web interface. The flaw allows attackers to upload malicious files with html extensions, which can then be executed within the context of other users' browsers when accessed through the elFinder functionality.
The technical implementation of this vulnerability involves a failure in input validation and file type restriction mechanisms within the Exponent CMS upload handler. When users attempt to upload files through the web interface, the system does not adequately verify the file extensions or content types against a whitelist of allowed formats. This weakness enables attackers to bypass security controls by uploading files with .html extensions that contain malicious javascript code. The elFinder component, which serves as the file browser and manager interface, then allows these uploaded files to be accessed and executed in the browser context of other users who visit the file locations. This creates a persistent cross-site scripting vector that can be exploited to steal session cookies, redirect users to malicious sites, or perform other harmful actions.
The operational impact of CVE-2015-8684 extends beyond simple XSS attacks, as the vulnerability can potentially enable more severe consequences including complete system compromise. Attackers can leverage this flaw to establish persistent access to the CMS environment, manipulate content, and potentially escalate privileges within the system. The vulnerability aligns with CWE-434, which describes insecure file upload vulnerabilities where applications allow file uploads without proper validation of file types, content, or location. From an adversary perspective, this vulnerability maps to ATT&CK technique T1059.007 for command and control through scripting and T1566 for social engineering via malicious file uploads. The impact is particularly concerning for organizations using Exponent CMS, as the vulnerability can be exploited without requiring authentication, making it accessible to anyone with access to the web application.
Organizations affected by this vulnerability should implement immediate mitigations including upgrading to Exponent CMS version 2.3.7 or later, which contains the necessary fixes for proper file type validation. Additionally, administrators should implement strict file type whitelisting for all upload functionality, ensuring that only safe file extensions such as images, documents, and other appropriate content types are accepted. The implementation of Content Security Policy headers can provide additional protection against XSS execution, while monitoring upload directories for suspicious files can help detect exploitation attempts. Security teams should also consider implementing web application firewalls to block suspicious upload attempts and regularly audit file upload functionality to prevent similar vulnerabilities from being introduced in future versions. The vulnerability demonstrates the critical importance of proper input validation and the principle of least privilege in file handling operations, as outlined in security best practices established by organizations such as the OWASP Foundation and NIST guidelines for secure coding practices.