What potential issue should be considered when using the 'HTTP_REFERER' variable in PHP?

The potential issue when using the 'HTTP_REFERER' variable in PHP is that it can be easily spoofed by malicious users, leading to security vulnerabilities such as CSRF attacks. To mitigate this risk, it is recommended to validate and sanitize the 'HTTP_REFERER' value before using it in any sensitive operations. 

$referer = isset($_SERVER['HTTP_REFERER']) ? $_SERVER['HTTP_REFERER'] : '';

// Validate and sanitize the referer URL
if (filter_var($referer, FILTER_VALIDATE_URL)) {
    // Proceed with using the referer value
} else {
    // Handle invalid referer URL
    echo "Invalid referer URL";
}

Keywords

HTTP_REFERER security vulnerability cross-site scripting validation

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