CVE-2025-52902 in filebrowser
Summary
by MITRE • 06/26/2025
File Browser provides a file managing interface within a specified directory and it can be used to upload, delete, preview, rename and edit files. The Markdown preview function of File Browser prior to v2.33.7 is vulnerable to Stored Cross-Site-Scripting (XSS). Any JavaScript code that is part of a Markdown file uploaded by a user will be executed by the browser. Version 2.33.7 contains a fix for the issue.
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Analysis
by VulDB Data Team • 07/10/2025
The vulnerability identified as CVE-2025-52902 affects File Browser, a web-based file management interface that enables users to perform various file operations including upload, delete, preview, rename, and edit functions. This application serves as a web-based file manager that provides a user-friendly interface for navigating and managing files within a specified directory structure. The vulnerability specifically targets the Markdown preview functionality, which allows users to view Markdown formatted content within the browser interface. The issue exists in versions prior to v2.33.7, making all earlier releases susceptible to exploitation by malicious actors who can leverage this flaw to execute arbitrary JavaScript code within the context of the victim's browser.
The technical flaw represents a stored cross-site scripting vulnerability that occurs when the Markdown preview function fails to properly sanitize user input before rendering content. When a user uploads a Markdown file containing malicious JavaScript code, this code becomes permanently stored within the application's file system and is subsequently executed whenever the file is previewed. The vulnerability stems from insufficient input validation and output encoding mechanisms within the Markdown rendering process, allowing attackers to inject malicious scripts that execute in the context of the authenticated user's browser session. This stored nature of the vulnerability means that the malicious payload persists even after the initial upload, making it particularly dangerous as it can affect multiple users who view the compromised files. The vulnerability aligns with CWE-079, which specifically addresses Cross-Site Scripting flaws, and represents a classic case of improper neutralization of input during web application development.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform various malicious activities within the context of the File Browser application. An attacker who successfully exploits this vulnerability can potentially steal session cookies, redirect users to malicious websites, modify file contents, or even escalate privileges within the application. The stored nature of the XSS vulnerability means that the attack vector can be maintained over time without requiring repeated exploitation attempts, making it particularly dangerous for environments where multiple users access the same file repository. This vulnerability undermines the security of the entire file management system, as any user with upload privileges can potentially compromise the application and affect all other users who might preview the malicious files. The impact is especially severe in collaborative environments where users trust the file management system and regularly preview various files.
Mitigation strategies for CVE-2025-52902 focus primarily on upgrading to version 2.33.7 or later, which contains the necessary patches to address the stored XSS vulnerability. Organizations should immediately implement this upgrade across all File Browser installations to eliminate the risk of exploitation. Additionally, administrators should consider implementing additional security controls such as input validation for file uploads, content security policies to prevent script execution, and regular security audits of uploaded files. The application should be configured with proper access controls to limit upload privileges to trusted users only, and automated scanning tools should be deployed to monitor for malicious file uploads. Network-level protections such as web application firewalls can provide additional defense in depth, though the primary solution remains the software upgrade. Security teams should also conduct user awareness training to educate staff about the risks of previewing untrusted files and the potential for malicious content in file uploads. This vulnerability demonstrates the critical importance of proper input sanitization and output encoding in web applications, aligning with ATT&CK technique T1566.001 for initial access through malicious files and T1059.007 for command and scripting interpreter through scriptlets, highlighting the need for comprehensive security measures throughout the application lifecycle.