Questions:
What are the best safe1(), safe2(), safe3(), and safe4() functions to avoid XSS for UTF8 encoded pages? Is it also safe in all browsers (specifically IE6)?
<body><?php echo safe1($xss)?></body>
<body id="<?php echo safe2($xss)?>"></body>
<script type="text/javascript">
var a = "<?php echo safe3($xss)?>";
</script>
<style type="text/css">
.myclass {width:<?php echo safe4($xss)?>}
</style>
.
Many people say the absolute best that can be done is:
// safe1 & safe2
$s = htmlentities($s, ENT_QUOTES, "UTF-8");
// But how would you compare the above to:
// https://github.com/shadowhand/purifier
// OR http://kohanaframework.org/3.0/guide/api/Security#xss_clean
// OR is there an even better if not perfect solution?
.
// safe3
$s = mb_convert_encoding($s, "UTF-8", "UTF-8");
$s = htmlentities($s, ENT_QUOTES, "UTF-8");
// How would you compare this to using using mysql_real_escape_string($s)?
// (Yes, I know this is a DB function)
// Some other people also recommend calling json_encode() before passing to htmlentities
// What's the best solution?
.
There are a hell of a lot of posts about PHP and XSS.
Most just say "use HTMLPurifier" or "use htmlspecialchars", or are wrong.
Others say use OWASP -- but it is EXTREMELY slow.
Some of the good posts I came across are listed below:
Do htmlspecialchars and mysql_real_escape_string keep my PHP code safe from injection?
XSS Me Warnings - real XSS issues?
CodeIgniter - why use xss_clean
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