What are the potential security risks associated with not validating user input before storing it in a PHP session?

If user input is not validated before storing it in a PHP session, it can lead to various security risks such as injection attacks, cross-site scripting (XSS), and data manipulation. To mitigate these risks, it is important to sanitize and validate user input before storing it in a session variable. 

// Validate and sanitize user input before storing it in a PHP session
if(isset($_POST['username'])) {
    $username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);
    $_SESSION['username'] = $username;
}

Keywords

SQL injection cross-site scripting session fixation data validation session hijacking

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