Summary

Vulnerability: Stored DOM Blind XSS via Backup Management Filename (Persistent Payload Injection)

• Stored Cross-Site Scripting (Blind XSS) via Unsanitized Backup Filename in Backup Management

Description

The application fails to properly sanitize user-controlled input when handling backup uploads and processing backup metadata. An attacker can inject a malicious JavaScript payload into the backup filename via the uploaded xss.sql, which uses SQL functionality to insert the XSS payload server-side.

This stored payload is later rendered unsafely in multiple backup management views without proper output encoding, leading to stored blind cross-site scripting (Blind XSS).

Affected Functionality

• Backup upload functionality
• Backup processing functionality
• Backup storage and retrieval logic

Attack Scenario

• An attacker uploads xss.sql which uses SQL functionality to insert a malicious XSS payload into the backup filename field server-side.
• The application stores this filename without sanitization or encoding.
• The payload persists and executes whenever the backup filename is rendered in affected views.
• The attacker does not see immediate execution, making this a Blind XSS scenario that triggers only when an administrator or privileged user views the backup management panel.

Impact

• Persistent Stored Blind XSS
• Execution of arbitrary JavaScript in victims’ browsers
• Privilege escalation when viewed by administrators or privileged users
• Full administrator account takeover
• Full account takeover across all roles
• Full compromise of the entire application

Endpoints:

• /backend/backup/upload
• /backend/backup/
• /backup/{id}

Steps To Reproduce (POC)

1. Upload xss.sql via the Backup Upload functionality
2. Ensure the SQL executes and inserts an XSS payload into the backup filename field such as: <img src=x onerror=alert(document.domain)>
3. Navigate to the Backup Management panel as an administrator
4. View the backup entry via the administrative panel
5. Notice the XSS payload executing automatically (Blind XSS)

Remediation

• Do not use , , or similar sink functions in client-side JavaScript or server-side templating (e.g., PHP). Even when user input flowing into these sinks is not immediately apparent, they can introduce Cross-Site Scripting (XSS) vulnerabilities that an attacker may exploit.