Determine if the server executes files based on their extension or if it filters specific dangerous strings.

Discovery often starts with identifying an upload form. In many "Zipper" style challenges, you find a PHP-based upload page that generates a download link for your compressed files.

: A ZIP file containing design assets (e.g., from remove.bg ) for web development.

Which of these scenarios matches the you are working with?

The application might be using ZipArchive in PHP to bundle files before storing them in an /uploads/ directory. Step 2: Exploitation (Webshell Upload)

To gain a foothold, you can bypass filters by uploading a simple PHP script (like a webshell) inside the zip process.

Because the server likely has an vulnerability or allows the use of PHP wrappers, you can call the file inside the archive without extracting it manually.