What potential security risks are present in the provided PHP code, and how can they be mitigated?

The provided PHP code is vulnerable to SQL injection attacks because it directly concatenates user input into the SQL query. To mitigate this risk, you should use prepared statements with parameterized queries to safely handle user input. 

// Original vulnerable code
$username = $_POST['username'];
$password = $_POST['password'];

$query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
$result = mysqli_query($connection, $query);

// Mitigated code using prepared statements
$stmt = $connection->prepare("SELECT * FROM users WHERE username=? AND password=?");
$stmt->bind_param("ss", $username, $password);
$stmt->execute();
$result = $stmt->get_result();

Keywords

SQL injection cross-site scripting CSRF password hashing input validation

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