What potential issues can arise when handling login sessions and user data in PHP, as highlighted in the provided code examples?

One potential issue that can arise when handling login sessions and user data in PHP is the lack of proper sanitization and validation of user input, which can lead to security vulnerabilities such as SQL injection or cross-site scripting attacks. To mitigate this risk, it is important to always sanitize and validate user input before using it in SQL queries or outputting it to the browser. 

// Example of sanitizing and validating user input before using it in a SQL query
$username = mysqli_real_escape_string($conn, $_POST['username']);
$password = mysqli_real_escape_string($conn, $_POST['password']);

// Perform validation on the input data
if (!empty($username) && !empty($password)) {
    // Proceed with the login process
} else {
    // Handle the case where input data is missing
}

Keywords

SQL injection session hijacking cross-site scripting password hashing CSRF protection

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