Feature #19600 » 0009778.patch
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* Used with permission by the author.
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* URL: http://quickwired.com/smallprojects/php_xss_filter_function.php
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*
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* 2008-09-29 : modifications by Jigal van Hemert:
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* - bugfixes in regexps
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* - optimizations
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* - quickscan for keywords to speed up the function when no potential threats
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* - regexps specific for different type of keywords to reduce false positives
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* - configurable "tag replaceString"
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* Check XSS attacks on: http://ha.ckers.org/xss.html
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*
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* License:
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* This code is public domain, you are free to do whatever you want with it,
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* $Id$
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*
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* @author Travis Puderbaugh <kallahar@quickwired.com>
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* @author Jigal van Hemert <jigal@xs4all.nl>
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* @package RemoveXSS
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*/
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class RemoveXSS {
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final class RemoveXSS {
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/**
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* Wrapper for the RemoveXSS function.
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* Removes potential XSS code from an input string.
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*
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* Using an external class by Travis Puderbaugh <kallahar@quickwired.com>
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*
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* @param string Input string
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* @return string Input string with potential XSS code removed
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*/
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function RemoveXSS($val) {
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* Wrapper for the RemoveXSS function.
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* Removes potential XSS code from an input string.
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*
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* Using an external class by Travis Puderbaugh <kallahar@quickwired.com>
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*
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* @param string Input string
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* @param string replaceString for inserting in keywords (which destroyes the tags)
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* @return string Input string with potential XSS code removed
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*/
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public function RemoveXSS($val, $replaceString='<x>') {
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// don't use empty $replaceString because then no XSS-remove will be done
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if ($replaceString == '') {
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$replaceString = '<x>';
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}
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// remove all non-printable characters. CR(0a) and LF(0b) and TAB(9) are allowed
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// this prevents some character re-spacing such as <java\0script>
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// note that you have to handle splits with \n, \r, and \t later since they *are* allowed in some inputs
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$val = preg_replace('/([\x00-\x08][\x0b-\x0c][\x0e-\x20])/', '', $val);
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$val = preg_replace('/([\x00-\x08][\x0b-\x0c][\x0e-\x19])/', '', $val);
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// straight replacements, the user should never need these since they're normal characters
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// this prevents like <IMG SRC=@avascript:alert('XSS')>
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$search = 'abcdefghijklmnopqrstuvwxyz';
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$search.= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
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$search.= '1234567890!@#$%^&*()';
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$search.= '~`";:?+/={}[]-_|\'\\';
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$search = '/&#[xX]0{0,8}(21|22|23|24|25|26|27|28|29|2a|2b|2d|2f|30|31|32|33|34|35|36|37|38|39|3a|3b|3d|3f|40|41|42|43|44|45|46|47|48|49|4a|4b|4c|4d|4e|4f|50|51|52|53|54|55|56|57|58|59|5a|5b|5c|5d|5e|5f|60|61|62|63|64|65|66|67|68|69|6a|6b|6c|6d|6e|6f|70|71|72|73|74|75|76|77|78|79|7a|7b|7c|7d|7e);?/ie';
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$val = preg_replace($search, "chr(hexdec('\\1'))", $val);
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$search = '/�{0,8}(33|34|35|36|37|38|39|40|41|42|43|45|47|48|49|50|51|52|53|54|55|56|57|58|59|61|63|64|65|66|67|68|69|70|71|72|73|74|75|76|77|78|79|80|81|82|83|84|85|86|87|88|89|90|91|92|93|94|95|96|97|98|99|100|101|102|103|104|105|106|107|108|109|110|111|112|113|114|115|116|117|118|119|120|121|122|123|124|125|126);?/ie';
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$val = preg_replace($search, "chr('\\1')", $val);
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for ($i = 0; $i < strlen($search); $i++) {
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// ;? matches the ;, which is optional
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// 0{0,7} matches any padded zeros, which are optional and go up to 8 chars
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// now the only remaining whitespace attacks are \t, \n, and \r
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$ra1 = array('javascript', 'vbscript', 'expression', 'applet', 'meta', 'xml', 'blink', 'link', 'style', 'script', 'embed', 'object', 'iframe', 'frame', 'frameset', 'ilayer', 'layer', 'bgsound', 'title', 'base', 'onabort', 'onactivate', 'onafterprint', 'onafterupdate', 'onbeforeactivate', 'onbeforecopy', 'onbeforecut', 'onbeforedeactivate', 'onbeforeeditfocus', 'onbeforepaste', 'onbeforeprint', 'onbeforeunload', 'onbeforeupdate', 'onblur', 'onbounce', 'oncellchange', 'onchange', 'onclick', 'oncontextmenu', 'oncontrolselect', 'oncopy', 'oncut', 'ondataavailable', 'ondatasetchanged', 'ondatasetcomplete', 'ondblclick', 'ondeactivate', 'ondrag', 'ondragend', 'ondragenter', 'ondragleave', 'ondragover', 'ondragstart', 'ondrop', 'onerror', 'onerrorupdate', 'onfilterchange', 'onfinish', 'onfocus', 'onfocusin', 'onfocusout', 'onhelp', 'onkeydown', 'onkeypress', 'onkeyup', 'onlayoutcomplete', 'onload', 'onlosecapture', 'onmousedown', 'onmouseenter', 'onmouseleave', 'onmousemove', 'onmouseout', 'onmouseover', 'onmouseup', 'onmousewheel', 'onmove', 'onmoveend', 'onmovestart', 'onpaste', 'onpropertychange', 'onreadystatechange', 'onreset', 'onresize', 'onresizeend', 'onresizestart', 'onrowenter', 'onrowexit', 'onrowsdelete', 'onrowsinserted', 'onscroll', 'onselect', 'onselectionchange', 'onselectstart', 'onstart', 'onstop', 'onsubmit', 'onunload');
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$ra_tag = array('applet', 'meta', 'xml', 'blink', 'link', 'style', 'script', 'embed', 'object', 'iframe', 'frame', 'frameset', 'ilayer', 'layer', 'bgsound', 'title', 'base');
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$ra_attribute = array('style', 'onabort', 'onactivate', 'onafterprint', 'onafterupdate', 'onbeforeactivate', 'onbeforecopy', 'onbeforecut', 'onbeforedeactivate', 'onbeforeeditfocus', 'onbeforepaste', 'onbeforeprint', 'onbeforeunload', 'onbeforeupdate', 'onblur', 'onbounce', 'oncellchange', 'onchange', 'onclick', 'oncontextmenu', 'oncontrolselect', 'oncopy', 'oncut', 'ondataavailable', 'ondatasetchanged', 'ondatasetcomplete', 'ondblclick', 'ondeactivate', 'ondrag', 'ondragend', 'ondragenter', 'ondragleave', 'ondragover', 'ondragstart', 'ondrop', 'onerror', 'onerrorupdate', 'onfilterchange', 'onfinish', 'onfocus', 'onfocusin', 'onfocusout', 'onhelp', 'onkeydown', 'onkeypress', 'onkeyup', 'onlayoutcomplete', 'onload', 'onlosecapture', 'onmousedown', 'onmouseenter', 'onmouseleave', 'onmousemove', 'onmouseout', 'onmouseover', 'onmouseup', 'onmousewheel', 'onmove', 'onmoveend', 'onmovestart', 'onpaste', 'onpropertychange', 'onreadystatechange', 'onreset', 'onresize', 'onresizeend', 'onresizestart', 'onrowenter', 'onrowexit', 'onrowsdelete', 'onrowsinserted', 'onscroll', 'onselect', 'onselectionchange', 'onselectstart', 'onstart', 'onstop', 'onsubmit', 'onunload');
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$ra_protocol = array('javascript', 'vbscript', 'expression');
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// @ @ search for the hex values
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$val = preg_replace('/(&#[x|X]0{0,8}'.dechex(ord($search[$i])).';?)/i', $search[$i], $val); // with a ;
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// @ @ 0{0,7} matches '0' zero to seven times
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$val = preg_replace('/(�{0,8}'.ord($search[$i]).';?)/', $search[$i], $val); // with a ;
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//remove the potential &#xxx; stuff for testing
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$val2 = preg_replace('/(&#[xX]?0{0,8}(9|10|13|a|b);)*\s*/i', '', $val);
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$ra = array();
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foreach ($ra1 as $ra1word) {
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//stripos is faster than the regular expressions used later
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//and because the words we're looking for only have chars < 0x80
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//we can use the non-multibyte safe version
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if (stripos($val2, $ra1word ) !== false ) {
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//keep list of potential words that were found
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if (in_array($ra1word, $ra_protocol)) {
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$ra[] = array($ra1word, 'ra_protocol');
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}
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if (in_array($ra1word, $ra_tag)) {
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$ra[] = array($ra1word, 'ra_tag');
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}
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if (in_array($ra1word, $ra_attribute)) {
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$ra[] = array($ra1word, 'ra_attribute');
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}
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//some keywords appear in more than one array
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//these get multiple entries in $ra, each with the appropriate type
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}
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}
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// now the only remaining whitespace attacks are \t, \n, and \r
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$ra1 = array('javascript', 'vbscript', 'expression', 'applet', 'meta', 'xml', 'blink', 'link', 'style', 'script', 'embed', 'object', 'iframe', 'frame', 'frameset', 'ilayer', 'layer', 'bgsound', 'title', 'base');
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$ra2 = array('onabort', 'onactivate', 'onafterprint', 'onafterupdate', 'onbeforeactivate', 'onbeforecopy', 'onbeforecut', 'onbeforedeactivate', 'onbeforeeditfocus', 'onbeforepaste', 'onbeforeprint', 'onbeforeunload', 'onbeforeupdate', 'onblur', 'onbounce', 'oncellchange', 'onchange', 'onclick', 'oncontextmenu', 'oncontrolselect', 'oncopy', 'oncut', 'ondataavailable', 'ondatasetchanged', 'ondatasetcomplete', 'ondblclick', 'ondeactivate', 'ondrag', 'ondragend', 'ondragenter', 'ondragleave', 'ondragover', 'ondragstart', 'ondrop', 'onerror', 'onerrorupdate', 'onfilterchange', 'onfinish', 'onfocus', 'onfocusin', 'onfocusout', 'onhelp', 'onkeydown', 'onkeypress', 'onkeyup', 'onlayoutcomplete', 'onload', 'onlosecapture', 'onmousedown', 'onmouseenter', 'onmouseleave', 'onmousemove', 'onmouseout', 'onmouseover', 'onmouseup', 'onmousewheel', 'onmove', 'onmoveend', 'onmovestart', 'onpaste', 'onpropertychange', 'onreadystatechange', 'onreset', 'onresize', 'onresizeend', 'onresizestart', 'onrowenter', 'onrowexit', 'onrowsdelete', 'onrowsinserted', 'onscroll', 'onselect', 'onselectionchange', 'onselectstart', 'onstart', 'onstop', 'onsubmit', 'onunload');
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$ra = array_merge($ra1, $ra2);
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$found = true; // keep replacing as long as the previous round replaced something
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while ($found == true) {
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$val_before = $val;
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for ($i = 0; $i < sizeof($ra); $i++) {
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$pattern = '/';
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for ($j = 0; $j < strlen($ra[$i]); $j++) {
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if ($j > 0) {
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$pattern .= '(';
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$pattern .= '(&#[x|X]0{0,8}([9][a][b]);?)?';
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$pattern .= '|(�{0,8}([9][10][13]);?)?';
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$pattern .= ')?';
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//only process potential words
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if (count($ra) > 0) {
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// keep replacing as long as the previous round replaced something
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$found = true;
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while ($found == true) {
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$val_before = $val;
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for ($i = 0; $i < sizeof($ra); $i++) {
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$pattern = '';
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for ($j = 0; $j < strlen($ra[$i][0]); $j++) {
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if ($j > 0) {
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$pattern .= '((&#[xX]0{0,8}([9ab]);)|(�{0,8}(9|10|13);)|\s)*';
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}
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$pattern .= $ra[$i][0][$j];
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}
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$pattern .= $ra[$i][$j];
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//handle each type a little different (extra conditions to prevent false positives a bit better)
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switch ($ra[$i][1]) {
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case 'ra_protocol':
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//these take the form of e.g. 'javascript:'
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$pattern .= '((&#[xX]0{0,8}([9ab]);)|(�{0,8}(9|10|13);)|\s)*(?=:)';
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break;
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case 'ra_tag':
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//these take the form of e.g. '<SCRIPT[^\da-z] ....';
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$pattern = '(?<=<)' . $pattern . '((&#[xX]0{0,8}([9ab]);)|(�{0,8}(9|10|13);)|\s)*(?=[^\da-z])';
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break;
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case 'ra_attribute':
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//these take the form of e.g. 'onload=' Beware that a lot of characters are allowed
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//between the attribute and the equal sign!
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$pattern .= '[\s\!\#\$\%\&\(\)\*\~\+\-\_\.\,\:\;\?\@\[\/\|\\\\\]\^\`]*(?==)';
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break;
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}
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$pattern = '/' . $pattern . '/i';
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// add in <x> to nerf the tag
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$replacement = substr_replace($ra[$i][0], $replaceString, 2, 0);
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// filter out the hex tags
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$val = preg_replace($pattern, $replacement, $val);
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if ($val_before == $val) {
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// no replacements were made, so exit the loop
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$found = false;
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}
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}
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$pattern .= '/i';
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$replacement = substr($ra[$i], 0, 2).'<x>'.substr($ra[$i], 2); // add in <> to nerf the tag
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$val = preg_replace($pattern, $replacement, $val); // filter out the hex tags
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if ($val_before == $val) {
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// no replacements were made, so exit the loop
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$found = false;
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}
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}
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}
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return $val;
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}
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}
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}
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?>
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