What potential security risks are associated with allowing HTML code to be posted in PHP scripts like a guestbook?

Allowing HTML code to be posted in PHP scripts like a guestbook can pose security risks such as cross-site scripting (XSS) attacks, where malicious code can be executed on other users' browsers. To mitigate this risk, you can use PHP's `htmlspecialchars()` function to escape any HTML tags before displaying user input on the page. This function converts special characters to their HTML entity equivalents, preventing the browser from interpreting them as code. 

// Escape HTML tags before displaying user input
$user_input = "<script>alert('XSS attack!');</script>";
echo htmlspecialchars($user_input);

Keywords

XSS SQL injection CSRF input validation escaping

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