Summary

Vulnerability: Stored DOM Blind XSS via Logs Interface Rendering (Administrative Context Execution)

• Stored Cross-Site Scripting (Blind XSS) via Unsafe Rendering of User-Controlled Logged Data

Description

The application renders user-controlled input unsafely within the logs interface. If any stored XSS payload exists within logged data, it is rendered without proper output encoding.

This issue becomes a Blind XSS scenario because the attacker does not see immediate execution. Instead, the payload is stored within application logs and only executes later when an administrator views the logs page.

For example, accessing /backend/backup/restore/xss-payload-here causes an error that gets logged by the application. If the injected portion contains an XSS payload, it is stored inside the logs without sanitization and later rendered unsafely inside the logs management interface.

When an administrator views the logs page, the stored payload executes automatically in the administrative browser context, leading to stored blind cross-site scripting (Blind XSS).

Affected Functionality

• Application logging mechanism
• Logs storage and retrieval logic
• Logs rendering within administrative interface
• Any endpoint that logs unsanitized user-controlled input

Attack Scenario

• An attacker injects a malicious XSS payload into any user-controlled input that is logged by the application.
• Example: Visit /backend/backup/restore/<img src=x onerror=alert(document.domain)>
• The application throws an error and logs the malicious payload.
• The payload is stored within application logs.
• An administrator views the logs interface.
• The payload executes automatically in the administrator’s browser context.

Any method or endpoint that logs user-controlled input without sanitization will result in the same Blind XSS condition when viewed inside logs management.

Impact

• Persistent Stored Blind XSS
• Execution of arbitrary JavaScript in administrators’ browsers
• Privilege escalation when viewed by administrators
• Full administrator account takeover
• Full compromise of the entire application

Endpoints:

• /backend/logs/
• /backend/backup/restore/{payload}
• Any other endpoint that logs xss payloads there

Steps To Reproduce (POC)

1. Trigger an endpoint that logs user-controlled input, such as:
   /backend/backup/restore/<img src=x onerror=alert(document.domain)>
2. Ensure the request generates an error and the payload is written into application logs
3. Navigate to the logs interface as an administrator
4. View the logged entry
5. Notice the XSS payload executing automatically (Blind XSS)

Remediation

• Never use .html() again or any innerHTML-style like JS in your PHP, or any other sink, even if user inputs that flow into them are not clear, they still represent real world danger as an attacker can make use of this to exploit the application via XSS. And do HTML Encoding as much as possible and always do Sanitization, theres no sanitization there unfortunately. Also apply CSP, HttpOnly, SameSite, and Secure upon all application, they reduce severity of XSS & escalated-CSRF via XSS and do great jobs

Ready Video POC:

https://mega.nz/file/jRN3nDSR#wJCwyFhbeT-OYAwlaTD_7j6wc5wRgz1EGJL0bnuhHxY