允许用户提供的<iframe>而不会有XSS的风险？

Question

My website is allowing blogging , i use textarea for the blog post and i need to allow the users to share things like youtube videos (i will need to allow iframe tag to do so) or display images using the img tag or using links by allowing the a tag , The problem is i need to secure the website against XXS attacks and that is why i am afraid to allow those tags, is there any work around to accomplish this ?

can i use something like this :

<?php
   $string = "<b>hello world!</b>";
   echo "without filtering:".$string;
   echo "<br>";
   $filtered = htmlspecialchars($string); // insert into database filtered
   echo "After filtering:".$filtered;
   echo "<br>";
   $de_filtering = htmlspecialchars_decode($filtered); //retrieve from database and display
   echo "After de-filtering:".$de_filtering;        
  ?>

is it possible to do that ?

Answer 1

The freshly released HTMPurifier 4.4 adds a feature for doing exactly this.

http://htmlpurifier.org/phorum/read.php?5,5319,5555#msg-5555

In short, you should allow iframes that come from trusted domains. Iframes from untrusted domains could include malicious javascript/flash/embeds