CVE-2026-35399: Wegia Wegia Stored XSS Vulnerability

CVE-2026-35399 Overview

CVE-2026-35399 is a stored Cross-Site Scripting (XSS) vulnerability affecting WeGIA, a web-based management system designed for charitable institutions. Prior to version 3.6.9, the application fails to properly sanitize user-supplied input in backup filenames, allowing attackers to inject malicious JavaScript code that persists in the application and executes when other users interact with the affected functionality.

This stored XSS vulnerability enables attackers to execute arbitrary scripts in the context of a victim's browser session, potentially leading to session hijacking, credential theft, or unauthorized actions performed on behalf of authenticated users.

Critical Impact

Attackers can inject persistent malicious scripts through backup filenames, enabling session hijacking and unauthorized actions in the context of authenticated users managing charitable institution data.

Affected Products

• WeGIA versions prior to 3.6.9
• WeGIA web management platform for charitable institutions
• All deployments running vulnerable WeGIA versions with backup functionality enabled

Discovery Timeline

• April 6, 2026 - CVE-2026-35399 published to NVD
• April 9, 2026 - Last updated in NVD database

Technical Details for CVE-2026-35399

Vulnerability Analysis

This stored XSS vulnerability (CWE-79) exists in WeGIA's backup management functionality, specifically in how the application handles and displays backup filenames. When a user creates or uploads a backup file, the filename is stored in the application's database without proper sanitization. Subsequently, when this filename is rendered in the user interface, the malicious script payload executes in the context of any user viewing the backup list or interacting with the affected backup file.

The attack requires no special privileges to execute initially—an attacker needs only the ability to create or manipulate backup files with crafted filenames. However, user interaction is required for the payload to trigger, as victims must navigate to portions of the application where the malicious filename is displayed and rendered by their browser.

The impact is significant in the context of charitable institution management, where the application likely handles sensitive donor information, financial records, and organizational data. A successful exploitation could allow attackers to steal session tokens, modify displayed content, redirect users to phishing pages, or perform administrative actions on behalf of compromised users.

Root Cause

The root cause of CVE-2026-35399 is improper input validation and output encoding in WeGIA's backup filename handling. The application accepts user-controlled input for backup filenames without sanitizing special characters that have semantic meaning in HTML/JavaScript contexts. When these filenames are later displayed in the web interface, they are rendered without proper output encoding, allowing embedded script tags or event handlers to execute as active code rather than being displayed as plain text.

Attack Vector

This vulnerability is exploitable over the network with low attack complexity. An attacker can craft a malicious backup filename containing JavaScript code, such as embedded <script> tags or event handler attributes. When this filename is stored and later displayed to other users—particularly administrators—the malicious code executes within their browser session.

The attack flow typically involves:

1. Attacker creates or modifies a backup file with a malicious filename containing XSS payload
2. The filename is stored in the WeGIA application database without sanitization
3. When an administrator or user navigates to the backup management interface, the filename is rendered
4. The victim's browser interprets the malicious content as executable code
5. The attacker's script runs with the victim's session privileges, potentially exfiltrating session cookies or performing unauthorized actions

For detailed technical information about the vulnerability mechanism and exploitation scenarios, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-35399

Indicators of Compromise

• Backup filenames containing HTML tags, JavaScript code, or event handlers such as <script>, onerror=, or onload=
• Unusual characters or encoded sequences in backup file names that may indicate XSS payloads
• Unexpected network requests originating from the WeGIA application to external domains
• Reports of unexpected behavior or redirects when users access backup management features

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block common XSS patterns in HTTP requests to backup-related endpoints
• Monitor application logs for backup operations involving filenames with suspicious characters or script content
• Deploy browser-based Content Security Policy (CSP) reporting to detect inline script execution attempts
• Review stored backup metadata in the database for entries containing potential XSS payloads

Monitoring Recommendations

• Enable verbose logging for all backup creation and management operations within WeGIA
• Configure alerts for any backup filenames containing angle brackets, script keywords, or JavaScript event handlers
• Monitor for anomalous session activity following user access to backup management features
• Implement file integrity monitoring on backup storage locations to detect unauthorized modifications

How to Mitigate CVE-2026-35399

Immediate Actions Required

• Upgrade WeGIA to version 3.6.9 or later immediately to address this vulnerability
• Review existing backup files for potentially malicious filenames and sanitize or remove suspicious entries
• Implement Content Security Policy (CSP) headers to mitigate the impact of any XSS exploitation
• Restrict access to backup management functionality to only essential administrative personnel

Patch Information

The vulnerability has been remediated in WeGIA version 3.6.9. Organizations should upgrade to this version or later to fully address the stored XSS vulnerability. The fix implements proper input validation and output encoding for backup filenames to prevent script injection.

For official patch details and release notes, consult the GitHub Security Advisory GHSA-fmwv-62wf-2hgx.

Workarounds

• If immediate patching is not possible, restrict access to backup functionality through application-level access controls or network segmentation
• Implement a Web Application Firewall (WAF) with XSS filtering rules to block malicious payloads in requests
• Manually sanitize existing backup filenames in the database by removing or encoding HTML/JavaScript characters
• Deploy Content Security Policy headers with strict script-src directives to prevent inline script execution

# Example CSP header configuration for Apache
# Add to .htaccess or httpd.conf to mitigate XSS impact
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; frame-ancestors 'self';"