GHSA-jhph-5q74-pmfx

Description

### Impact A low-privilege user can store an active-content payload as an asset attachment and have it served inline, same-origin, with an active Content-Type, achieving stored XSS. The application sanitizes uploads only when PHP finfo detects image/svg+xml. By submitting an XHTML document whose finfo MIME is text/xml (an allowed extension), the svg-sanitize branch is skipped, the <script> is stored raw, and the inline-serve path returns it as text/xml; charset=utf-8 with Content-Disposition: inline — which the browser renders as a live XHTML document and executes. The dedicated StorageHelper::allowSafeInline() whitelist that should have constrained inline-renderable types is never wired into the serve path. ### Details Vulnerable code — sanitizer keyed on finfo MIME `app/Http/Requests/UploadFileRequest.php:46-53` ```php $extension = $file->getClientOriginalExtension(); $file_name = $name_prefix.'-'.str_random(8).'-'.str_slug(...).'.'.$file->guessExtension(); ... if ($file->getMimeType() === 'image/svg+xml') { $uploaded_file = $this->handleSVG($file); // svg-sanitize fires } else { $uploaded_file = file_get_contents($file); // stored RAW — no sanitization } ``` Vulnerable code — inline serve, no `allowSafeInline()` `app/Http/Controllers/UploadedFilesController.php:103` ```php if (request('inline') == 'true') { $headers = ['Content-Disposition' => 'inline']; return Storage::download($path.$log->filename, $log->filename, $headers); } ``` `StorageHelper::allowSafeInline()` (`app/Helpers/StorageHelper.php:88`) exists to whitelist inline-renderable types but is not called here. The validation rule (`UploadFileRequest::rules()`) is `mimes`: over `config('filesystems.allowed_upload_extensions_for_validator')`, which includes svg, xml, and txt — so a text/xml file passes validation and bypasses the SVG sanitizer simultaneously. POC 1. From a fresh install, as a user with only `assets.view` + `assets.files` targeting any existing asset created by admin 2. click on the asset created by admin and upload files. 3. create a XML file with the following payload and upload it. ```xml <?xml version="1.0"?> <html xmlns="http://www.w3.org/1999/xhtml"> <head><script>alert(document.cookie)</script></head> <body>hi</body> </html> ``` 4. Noticed that it did not receive any error and the file was uploaded. 5. Now, can just get the URL and view it. (need to add the `inline=true`). image.png Notice that the XSS was able to request `document.cookie`. This means that it is possible for low privilege user to perform XSS and perform privilege escalation to admin.