What are some common security risks associated with handling user input in PHP, as seen in the provided code snippet?

One common security risk associated with handling user input in PHP is the vulnerability to SQL injection attacks. This occurs when user input is directly concatenated into SQL queries without proper sanitization. To mitigate this risk, it is important to use prepared statements with parameterized queries to prevent malicious SQL injection attempts. 

// Original code with SQL injection vulnerability
$user_input = $_POST['username'];
$query = "SELECT * FROM users WHERE username = '$user_input'";
$result = mysqli_query($connection, $query);

// Fixed code using prepared statements
$user_input = $_POST['username'];
$query = "SELECT * FROM users WHERE username = ?";
$stmt = mysqli_prepare($connection, $query);
mysqli_stmt_bind_param($stmt, "s", $user_input);
mysqli_stmt_execute($stmt);
$result = mysqli_stmt_get_result($stmt);

Keywords

SQL injection cross-site scripting input validation data sanitization security vulnerabilities

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