Exam CS0-003 topic 1 question 329 discussion

This php command essentially tells the server to retrieve input from an HTTP request with xyz as the key and execute any arbitrary command input into that xyz key. The "echo ""; die;" tells the server to only send back output from the command, stripping away any web page content. If this is successfully executed, the attacker could send a request at any time such as "https://example.com/example.php?xyz=cat+/etc/passwd" and the server would reveal the contents of the passwd file. This is effectively a RCE backdoor