EasyAdmin: Stored Cross-Site Scripting (XSS) via uploaded files served inline in FileField and ImageField

EasyAdmin is a fast and modern admin generator for Symfony applications. From 5.0.0 until 5.0.13, FileField and ImageField can accept browser-executable uploads while templates/crud/field/file.html.twig links to stored files for inline same-origin rendering without a download attribute or Content-Disposition attachment header. When uploads are stored under the public web root, an attacker with access to an affected form can upload HTML through FileField or SVG through ImageField, and JavaScript executes in an authenticated administrator's origin when the file is opened from the backend. Exploitation requires a privilege gap between the uploader and viewer. The issue can expose session or CSRF tokens and enable privilege escalation, but does not permit PHP or PHTML code execution because Symfony guessExtension does not produce those stored extensions. This issue is fixed in version 5.0.13.