Bypass MIME Checks

How to Execute the Bypass

Because the validation relies purely on a text string inside the request, bypassing it is trivial. You just need to change the text. 1. Intercept: Turn on your proxy's intercept feature and upload your shell.php file through the web browser. 2. Catch & Modify: The proxy pauses the request before it leaves your machine. Locate the line that says Content-Type: application/x-php just below your filename. 3. Spoof: Delete application/x-php and replace it with an allowed MIME type, such as image/png or image/jpeg. 4. Forward: Send the modified request to the server. The server's PHP script checks the header, sees image/png, evaluates the security check as true, and happily saves shell.php to the server.