function RemoveXSS($val) { // remove all non-printable
characters. CR(0a) and LF(0b) and TAB(9) are allowed // this prevents
some character re-spacing such as <java\0script> // note that you
have to handle splits with \n, \r, and \t later since they *are* allowed
in some inputs $val =
preg_replace('/([\x00-\x08][\x0b-\x0c][\x0e-\x20])/', '', $val);
// straight replacements, the user should never need these since
they're normal characters // this prevents like <IMG
SRC=@avascript:a& _#X6Cert('XSS')>
$search = 'abcdefghijklmnopqrstuvwxyz'; $search .=
'ABCDEFGHIJKLMNOPQRSTUVWXYZ'; $search .= '1234567890!@#$%^&*()';
$search .= '~`";:?+/={}[]-_|\'\\'; for ($i = 0; $i <
strlen($search); $i++) { // ;? matches the ;, which is optional
// 0{0,7} matches any padded zeros, which are optional and go up to
8 chars
// @ @ search for the hex values $val =
preg_replace('/(&#[x|X]0{0,8}'.dechex(ord($search[$i])).';?)/i',
$search[$i], $val); // with a ; // @ @ 0{0,7} matches '0'
zero to seven times $val =
preg_replace('/(�{0,8}'.ord($search[$i]).';?)/', $search[$i], $val);
// with a ; }