exec

The exec function in PHP is used to execute an external program or a shell command from within a PHP script. It provides a powerful way to interact with the underlying operating system. However, this capability comes with significant security risks if not used carefully.

exec allows a PHP script to run shell commands or external programs and optionally collect the last line of the output.

The primary security concern with exec is the risk of command injection attacks. If user input is not properly sanitized, an attacker can inject malicious commands to be executed by the server, leading to severe vulnerabilities like remote code execution.

If the use of exec is not tightly controlled, it can allow attackers to execute arbitrary commands on the server, potentially gaining unauthorized access to the system, modifying files, or accessing sensitive data.

PHP provides other functions to execute shell commands, like shell_exec, system, and passthru, each with slightly different behavior. However, these functions have similar security risks and must be used with caution.