What are the potential security risks associated with the current implementation of the login function?

The potential security risks associated with the current implementation of the login function include SQL injection attacks and brute force attacks. To mitigate these risks, we should use prepared statements to prevent SQL injection and implement account lockout mechanisms to prevent brute force attacks. 

// Using prepared statements to prevent SQL injection
$stmt = $pdo->prepare("SELECT * FROM users WHERE username = :username AND password = :password");
$stmt->execute(['username' => $username, 'password' => $password]);
$user = $stmt->fetch();

// Implementing account lockout mechanism to prevent brute force attacks
if ($user) {
    // Login successful
} else {
    // Increment login attempts for the user
    $loginAttempts = $user['login_attempts'] + 1;
    $stmt = $pdo->prepare("UPDATE users SET login_attempts = :loginAttempts WHERE username = :username");
    $stmt->execute(['loginAttempts' => $loginAttempts, 'username' => $username]);

    if ($loginAttempts >= 3) {
        // Lock the user account
        $stmt = $pdo->prepare("UPDATE users SET is_locked = 1 WHERE username = :username");
        $stmt->execute(['username' => $username]);
    }

    // Display error message to the user
}

Keywords

SQL injection cross-site scripting session hijacking password hashing secure coding practices

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