What potential security risks should be considered when allowing external systems to interact with PHP scripts?

When allowing external systems to interact with PHP scripts, potential security risks include SQL injection, cross-site scripting (XSS), and remote code execution. To mitigate these risks, input validation, sanitization, and parameterized queries should be used to prevent malicious input from being executed. Additionally, limiting the permissions of the PHP script and implementing proper authentication mechanisms can help protect against unauthorized access. 

// Example of input validation and parameterized query to prevent SQL injection

// Assuming $db is the database connection object

// Validate and sanitize input
$user_input = $_POST['user_input'];
$clean_input = filter_var($user_input, FILTER_SANITIZE_STRING);

// Prepare and execute parameterized query
$stmt = $db->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $clean_input);
$stmt->execute();
$result = $stmt->get_result();

// Process the query result
while ($row = $result->fetch_assoc()) {
    // Handle the results
}

$stmt->close();
$db->close();

Keywords

SQL injection Cross-site scripting (XSS) CSRF (Cross-Site Request Forgery) Input validation Authentication.

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