What potential issues can arise when passing user input values directly into HTML attributes in PHP?

Passing user input values directly into HTML attributes in PHP can lead to security vulnerabilities such as cross-site scripting (XSS) attacks. To prevent this, it is important to properly sanitize and validate user input before outputting it to the HTML attributes. 

<?php
$user_input = "<script>alert('XSS attack!');</script>";
$sanitized_input = htmlspecialchars($user_input, ENT_QUOTES, 'UTF-8');
echo "<input type='text' value='$sanitized_input'>";
?>

Keywords

XSS security vulnerabilities htmlspecialchars htmlentities input validation

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