Stored XSS via <iframe> in HAX CMS allows access to sensitive client-side data and account takeover

### Summary A stored cross-site scripting (XSS) vulnerability exists in HAX CMS due to improper sanitization of `<iframe>` elements. The application allows `javascript:` URIs in the `src` attribute, which are executed when a malicious page is viewed. This enables attackers to execute arbitrary JavaScript in the context of the victim’s browser and access sensitive data exposed to client-side scripts. ### Details Successful exploitation allows access to any data available in the browser context, including: - Authentication tokens (e.g., JWT) - Session cookies (if not protected with HttpOnly) - Application configuration (e.g., window.appSettings) - User-specific data accessible via APIs This significantly increases the impact beyond simple script execution. ### PoC Steps to reproduce: 1. Log in to HAX CMS as any authenticated user. 2. Create a new page or edit an existing page. 3. Open the HTML source editor (`<>`). 4. Insert the following payload: ```html <iframe srcdoc="&lt;script&gt; (function(){ try { var jwt = parent.window.appSettings.jwt; alert('Stolen JWT:\n' + jwt); } catch(e) { alert('Error: ' + e.message); } })(); &lt;/script&gt;" style="display:none" sandbox="allow-scripts allow-same-origin"></iframe> ``` <img width="2446" height="1319" alt="image" src="https://github.com/user-attachments/assets/daea3b41-8c72-4f6c-ab32-34c688bbd251" /> <img width="2464" height="1397" alt="image" src="https://github.com/user-attachments/assets/911cbd42-db50-454a-b178-51555e0db79c" /> <img width="2466" height="1409" alt="webhook`" src="https://github.com/user-attachments/assets/8a286435-98f4-418c-a596-d0c19556696a" /> ### Impact This vulnerability allows stored XSS leading to: - Execution of arbitrary JavaScript in victim browsers - Access to sensitive client-side data, including authentication tokens and session identifiers - Unauthorized API actions performed on behalf of the victim - Session hijacking and full account takeover Because the application exposes authentication data in the client-side environment, exploitation of this vulnerability can lead to complete compromise of user accounts and site content.