Description

REDAXO has reflected XSS backend packages API via function parameter (CSRF token required)

Summary

A reflected XSS vulnerability has been identified in the REDAXO backend. The function parameter is concatenated into an API error message and rendered without HTML escaping.

Details

Root cause User input function is injected into an exception message, then rendered by rex_view::error() which delegates to rex_view::message() without HTML escaping.

Vulnerable code (redaxo/src/core/lib/packages/api_package.php) :

$function = rex_request('function', 'string');
throw new rex_api_exception('Unknown package function "' . $function . '"!');

Sink (redaxo/src/core/lib/view.php) :

return '<div class="' . $cssClassMessage . '">' . $message . '</div>';

Source -> sink flow

Source: function (GET)

Propagation: concatenated into the exception message

Sink: rendered via rex_view::error() -> rex_view::message() without escaping

Authentication required: yes (backend session)

PoC - Exploit

#!/usr/bin/env python3
import re
import urllib.parse
import requests

TARGET_URL = "http://poc.local/"
BACKEND_PATH = "redaxo/index.php"
...
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To run the PoC you must set a valid admin account PHPSSID. The PoC will then automatically retrieve the CSRF token and generate a ready-to-use exploitation link.

Impact

Confidentiality: Low : no direct session theft (HttpOnly cookies), but possibility to access/exfiltrate data available via the DOM or via same-origin requests if the XSS executes in a victim’s session.

Integrity: Low : possibility to chain backend actions on behalf of the user (same-origin requests) only if execution takes place in a victim session; otherwise the impact is limited to the user who triggers the call.

Availability: Low : the XSS could disrupt the administration interface or trigger unwanted actions, but the token requirement strongly limits realistic scenarios.

Demo

https://github.com/user-attachments/assets/41d0186a-7ca0-4482-86c5-8bea6c8f6ac6

Mitigation

Aliases

References