GHSA-r736-2678-fcrx FacturaScripts vulnerable to stored XSS via product reference in sales/purchases

• Packagist facturascripts/facturascripts: <= 2025.92 (no fix yet)

Summary A stored Cross-Site Scripting (XSS) vulnerability exists in the product search modal of sales and purchases documents. An authenticated user with access to the warehouse module can create a product with a malicious reference that executes arbitrary JavaScript in the browser of any other user who opens the product search modal inside an invoice, order, or delivery note. Affected files • `Core/Lib/AjaxForms/SalesModalHTML.php` • `Core/Lib/AjaxForms/PurchasesModalHTML.php` Vulnerability details The `referencia` field of a product variant is injected directly into an HTML `onclick` attribute string without JavaScript context escaping: ```php // SalesModalHTML.php ~line 102 $tbody .= ''; ``` When a product is saved, `noHtml()` encodes `'` → `&#39;`. This appears safe in static HTML context. However, the modal HTML is later returned as a JSON response and inserted into the DOM via `innerHTML`: ```javascript // SalesDocument.html.twig line 118 document.getElementById("findProductList").innerHTML = data.products; ``` The browser HTML parser decodes `&#39;` → `'` during the `innerHTML` assignment, breaking out of the JavaScript string literal in the `onclick` attribute and executing the injected code. Attack payload stored in database: `x&#39;+alert(1)+&#39;` Resulting `onclick` after `innerHTML` decode: ```javascript return salesFormAction('add-product', 'x'+alert(1)+'') // ^^^^^^^^^^ executes before the function call ``` Steps to reproduce Step 1 — Inject the payload 1. Log in as a user with write access to Warehouse → Products 2. Navigate to `/EditProducto` and create a new product with the following values: | Field | Value | |---|---| | Reference | `x'+alert(1)+'` | | Description | `test` | 3. Save the product Step 2 — Trigger the XSS 1. Make sure at least one customer exists in the system (Sales → Customers) 2. Navigate to `/EditFacturaCliente?codcliente=` 3. In the invoice form, click the product search button next to the "Referencia" field 4. Click on the 'malicious' product `alert(1)` Impact Although session cookies (`fsLogkey`, `fsNick`) have the `HttpOnly` flag set and cannot be read directly via `document.cookie`, the injected script runs in the victim's authenticated browser context, meaning the attacker can make arbitrary authenticated requests on their behalf, create new admin users via AJAX POST to `/EditUser`, exfiltrate any business data visible in the DOM, or redirect the user to an external site. The most critical scenario is privilege escalation: a low-privilege employee with only warehouse access can execute JavaScript in an administrator's session without knowing their password. Recommended fix Apply `htmlspecialchars()` with `ENT_QUOTES` before inserting `referencia` into the `onclick` attribute in both affected files. `Core/Lib/AjaxForms/SalesModalHTML.php` ```php // Before (vulnerable): $tbody .= ''; // After (safe): $tbody .= ''; ``` `Core/Lib/AjaxForms/PurchasesModalHTML.php` Apply the same change to the equivalent line. Why `ENT_QUOTES` is required: `ENT_QUOTES` encodes both `"` and `'` characters. This ensures that `'` is stored as `&#39;` and — critically — remains `&#39;` after `innerHTML` assignment, because `htmlspecialchars` produces a form that the HTML parser does not decode back into a raw quote inside a JS string context. Alternative mitigation: replace `innerHTML` with `innerText` or a DOM-based rendering approach that never parses injected strings as HTML. This would eliminate the entire class of HTML-injection-via-innerHTML vulnerabilities in the sales and purchases forms. Credits Omar Ramirez