Part 3 of 4 — Laravel Architecture Patterns for Production ~9 min read · Security · Middleware · File handling A file upload is the moment you hand control to an untrusted user. Everything else in your application — form inputs, query parameters, JSON — is text. You validate it, sanitize it, store it in a database. A file upload is arbitrary binary data from a source you cannot verify, about to be written to your filesystem. The surface area is different. The failure modes are different. The consequences are different. Most tutorials cover the happy path: accept the file, store it, return a URL. The problem is never the happy path. Rename a PHP file to image.jpg . Upload it. Many Laravel applications accept it — because getClientOriginalExtension() returns jpg and getClientMimeType() returns image/jpeg . Both values the client provided. Neither verified by the server. This is how webshells get uploaded. This is how stored XSS gets planted in SVG files. This is the gap.…