Program: CWE-79
Project: CVE-2017-9305
Buggy source:
<?php
// (c) Copyright 2002-2016 by authors of the Tiki Wiki CMS Groupware Project
//
// All Rights Reserved. See copyright.txt for details and a complete list of authors.
// Licensed under the GNU LESSER GENERAL PUBLIC LICENSE. See license.txt for details.
// $Id$

class TikiFilter_PreventXss implements Zend\Filter\FilterInterface
{
	function filter( $value )
	{
		// No need to filter really simple values
		if ( ctype_alnum($value) || empty($value) )
			return $value;
		else
			return $this->RemoveXSS($value);
	}

	/* RemoveXSS initially developped by kallahar - quickwired.com, modified for Tiki
	 * Original code could be found here:
	 * http://quickwired.com/smallprojects/php_xss_filter_function.php
	 */
	function RemoveXSS($val)
	{
		static $ra_as_tag_only = NULL;
		static $ra_as_attribute = NULL;
		static $ra_as_content = NULL;
		static $ra_javascript = NULL;

		// now the only remaining whitespace attacks are \t, \n, and \r
		if ( $ra_as_tag_only == NULL ) {
			$ra_as_tag_only = array(
                'style',
                'script',
                'embed',
                'object',
                'applet',
                'meta',
                'iframe',
                'frame',    // also filters frameset
                'ilayer',
                'layer',
                'bgsound',
                'base',
                'xml',
                'import',
                'link',
                'audio',
                'video'
			);


			// note: short forms, such as onmouse, will filter its long forms:　onmouseup, onmousedown etc.
			$ra_as_attribute = array(
                'onabort',
                'onactivate',
                'onafter',
                'onbefore',
                'onbegin',
                'onblur',
                'onbounce',
                'onbroadcast',
                'oncellchange',
                'onchange',
                'onclick',
                'onclose',
                'oncommand',
                'oncontextmenu',
                'oncontrolselect',
                'oncopy',
                'oncut',
                'ondata',
                'ondblclick',
                'ondeactivate',
                'ondrag',
                'ondrop',
                'onend',
                'onerror',
                'onfilterchange',
                'onfinish',
                'onfocus',
                'ongotpointer',
                'onhashchange',
                'onhelp',
                'oninput',
                'oninvalid',
                'onkey',
                'onlayoutcomplete',
                'onload',
                'onlosecapture',
                'onlostpointer',
                'onmedia',
                'onmessage',
                'onmouse',
                'onmove',
                'onoffline',
                'ononline',
                'onoutofsync',
                'onover',
                'onpage',
                'onpaste',
                'onpause',
                'onpointer',
                'onpopstate',
                'onprogress',
                'onpropertychange',
                'onreadystatechange',
                'onredo',
                'onrepeat',
                'onreset',
                'onresize',
                'onresume',
                'onreverse',
                'onrow',
                'onunder',
                'onscroll',
                'onseek',
                'onsearch',
                'onselect',
                'onstart',
                'onshow',
                'onstop',
                'onstorage',
                'onsyncrestored',
                'onsubmit',
                'ontimeerror',
                'ontoggle',
                'ontouch',
                'ontrackchange',
                'onundo',
                'onunload',
                'onurlflip',
                'onwheel',
                'onpopup',
                'codebase',
                'dynsrc',
                'lowsrc',
                'xmlns'
			);

			$ra_as_content = array('vbscript', 'eval');
			$ra_javascript = array('javascript');
	///		$ra_style = array('style'); // Commented as it has been considered as a bit too aggressive
		}

		// keep replacing as long as the previous round replaced something
		while ( $this->RemoveXSSchars($val)
			|| $this->RemoveXSSregexp($ra_as_tag_only, $val, '(\<|\[\\\\xC0\]\[\\\\xBC\])\??')
			|| $this->RemoveXSSregexp($ra_as_attribute, $val)
			|| $this->RemoveXSSregexp($ra_as_content, $val, '[\.\\\\+\*\?\[\^\]\$\(\)\{\}\=\!\<\|\:;\-\/`#"\']', '(?!\s*[a-z0-9])', true)
			|| $this->RemoveXSSregexp($ra_javascript, $val, '', ':', true)
	///		|| RemoveXSSregexp($ra_style, $val, '[^a-z0-9]', '=') // Commented as it has been considered as a bit too aggressive
		);

		return $val;
	}

	function RemoveXSSchars(&$val)
	{
		static $patterns = NULL;
		static $replacements = NULL;
		$val_before = $val;
		$found = true;

		if ( $patterns == NULL ) {
			$patterns = array();
			$replacements = array();

			// 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
			$patterns[] = '/([\x00-\x08\x0b-\x0c\x0e-\x19])/';
			$replacements[] = '';

			// straight replacements, the user should never need these since they're
			// normal characters this prevents like
			// <IMG SRC=&#X40&#X61&#X76&#X61&#X73&#X63&#X72&#X69&#X70&#X74&#X3A&#X61&#X6C&#X65&#X72&#X74&#X28&#X27&#X58&#X53&#X53&#X27&#X29>
			// Calculate the search and replace patterns only once
			$search = 'abcdefghijklmnopqrstuvwxyz';
			$search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
			$search .= '1234567890!@#$%^&*()';
			$search .= '~`";:?+/={}[]-_|\'\\';
			for ($i = 0, $istrlen_search = strlen($search); $i < $istrlen_search; $i++) {
				// ;? matches the ;, which is optional
				// 0{0,8} matches any padded zeros,
				// which are optional and go up to 8 chars
				// &#x0040 @ search for the hex values
				$patterns[] = '/(&#[xX]0{0,8}'.dechex(ord($search[$i])).';?)/i';
				$replacements[] = $search[$i];
				// &#00064 @ 0{0,8} matches '0' zero to eight times
				// with a ;
				$patterns[] = '/(&#0{0,8}'.ord($search[$i]).';?)/';
				$replacements[] = $search[$i];
			}
		}
		$val = preg_replace($patterns, $replacements, $val);
		if ($val_before == $val) {
			// no replacements were made, so exit the loop
			$found = false;
		}
		return $found;
	}

	function RemoveXSSregexp(&$ra, &$val, $prefix = '', $suffix = '', $allow_spaces = false)
	{
		$val_before = $val;
		$found = true;
		$patterns = array();
		$replacements = array();

		$pattern_sep = '('
			.'&#[xX]0{0,8}[9ab];?'
			.'|&#0{0,8}(9|10|13);?'
			.'|(?ms)(\/\*.*?\*\/|\<\!\-\-.*?\-\-\>)'
			.'|(\<\!\[CDATA\[|\]\]\>)'
			.'|\\\\?'
			.( $allow_spaces ? '|\s' : '' )
		.')*';

		$pattern_start = '/';
		if ( $prefix != '' ) {
			$pattern_start .= '(' . $prefix . '\s*' . $pattern_sep . ')';
		}

		$pattern_end = '/i';
		if ( $suffix != '' ) {
			if ( $suffix == '=' || $suffix == ':' ) {
				$replacement_end = $suffix;
				$pattern_end = '(' . $pattern_sep . '\s*' . $suffix . ')' . $pattern_end;
			} else {
				$replacement_end = '';
				$pattern_end = $suffix . $pattern_end;
			}
		} else {
			$replacement_end = '';
		}

		for ($i = 0, $isizeof_ra = count($ra); $i < $isizeof_ra; $i++) {
			$pattern = $pattern_start;
			for ($j = 0, $jstrlen_rai = strlen($ra[$i]); $j < $jstrlen_rai; $j++) {
				if ($j > 0) {
					$pattern .= $pattern_sep;
				}
				$pattern .= $ra[$i][$j];
			}
			$pattern .= $pattern_end;
			$replacement = ( $prefix != '' ) ? '\\1' : '';
			// add in <> to nerf the tag
			$replacement .= substr($ra[$i], 0, 2).'<x>'.substr($ra[$i], 2);
			$patterns[] = $pattern;
			$replacements[] = $replacement.$replacement_end;
		}
		// filter out the hex tags
		$val = preg_replace($patterns, $replacements, $val);

		if ($val === null) {
			Feedback::error(tr('Filter error: "%0"', 
				array_flip(get_defined_constants(true)['pcre'])[preg_last_error()]), 'session');
		}
		if ($val_before == $val) {
			// no replacements were made, so exit the loop
			$found = false;
		}

		return $found;
	}
}


Fixed version (ground truth):
<?php
// (c) Copyright 2002-2016 by authors of the Tiki Wiki CMS Groupware Project
//
// All Rights Reserved. See copyright.txt for details and a complete list of authors.
// Licensed under the GNU LESSER GENERAL PUBLIC LICENSE. See license.txt for details.
// $Id$

class TikiFilter_PreventXss implements Zend\Filter\FilterInterface
{
	function filter( $value )
	{
		// No need to filter really simple values
		if ( ctype_alnum($value) || empty($value) )
			return $value;
		else
			return $this->RemoveXSS($value);
	}

	/* RemoveXSS initially developped by kallahar - quickwired.com, modified for Tiki
	 * Original code could be found here:
	 * http://quickwired.com/smallprojects/php_xss_filter_function.php
	 */
	function RemoveXSS($val)
	{
		static $ra_as_tag_only = NULL;
		static $ra_as_attribute = NULL;
		static $ra_as_content = NULL;
		static $ra_javascript = NULL;

		// now the only remaining whitespace attacks are \t, \n, and \r
		if ( $ra_as_tag_only == NULL ) {
			$ra_as_tag_only = array(
                'style',
                'script',
                'embed',
                'object',
                'applet',
                'meta',
                'iframe',
                'frame',    // also filters frameset
                'ilayer',
                'layer',
                'bgsound',
                'base',
                'xml',
                'import',
                'link',
                'audio',
                'video'
			);


			// note: short forms, such as onmouse, will filter its long forms:　onmouseup, onmousedown etc.
			$ra_as_attribute = array(
                'onabort',
                'onactivate',
                'onafter',
                'onbefore',
                'onbegin',
                'onblur',
                'onbounce',
                'onbroadcast',
                'oncellchange',
                'onchange',
                'onclick',
                'onclose',
                'oncommand',
                'oncontextmenu',
                'oncontrolselect',
                'oncopy',
                'oncut',
                'ondata',
                'ondblclick',
                'ondeactivate',
                'ondrag',
                'ondrop',
                'onend',
                'onerror',
                'onfilterchange',
                'onfinish',
                'onfocus',
                'ongotpointer',
                'onhashchange',
                'onhelp',
                'oninput',
                'oninvalid',
                'onkey',
                'onlayoutcomplete',
                'onload',
                'onlosecapture',
                'onlostpointer',
                'onmedia',
                'onmessage',
                'onmouse',
                'onmove',
                'onoffline',
                'ononline',
                'onoutofsync',
                'onover',
                'onpage',
                'onpaste',
                'onpause',
                'onpointer',
                'onpopstate',
                'onprogress',
                'onpropertychange',
                'onreadystatechange',
                'onredo',
                'onrepeat',
                'onreset',
                'onresize',
                'onresume',
                'onreverse',
                'onrow',
                'onunder',
                'onscroll',
                'onseek',
                'onsearch',
                'onselect',
                'onstart',
                'onshow',
                'onstop',
                'onstorage',
                'onsyncrestored',
                'onsubmit',
                'ontimeerror',
                'ontoggle',
                'ontouch',
                'ontrackchange',
                'onundo',
                'onunload',
                'onurlflip',
                'onwheel',
                'onpopup',
                'codebase',
                'dynsrc',
                'lowsrc',
                'xmlns'
			);

			$ra_as_content = array('vbscript', 'eval');
			$ra_javascript = array('javascript');
	///		$ra_style = array('style'); // Commented as it has been considered as a bit too aggressive
		}

		// keep replacing as long as the previous round replaced something
		while ( $this->RemoveXSSchars($val)
			|| $this->RemoveXSSregexp($ra_as_tag_only, $val, '(\<|\[\\\\xC0\]\[\\\\xBC\])\??')
			|| $this->RemoveXSSregexp($ra_as_attribute, $val)
			|| $this->RemoveXSSregexp($ra_as_content, $val, '[\.\\\\+\*\?\[\^\]\$\(\)\{\}\=\!\<\|\:;\-\/`#"\']', '(?!\s*[a-z0-9])', true)
			|| $this->RemoveXSSregexp($ra_javascript, $val, '', ':', true)
	///		|| RemoveXSSregexp($ra_style, $val, '[^a-z0-9]', '=') // Commented as it has been considered as a bit too aggressive
		);

		return $val;
	}

	function RemoveXSSchars(&$val)
	{
		static $patterns = NULL;
		static $replacements = NULL;
		$val_before = $val;
		$found = true;

		if ( $patterns == NULL ) {
			$patterns = array();
			$replacements = array();

			// 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
			$patterns[] = '/([\x00-\x08\x0b-\x0c\x0e-\x19])/';
			$replacements[] = '';

			// straight replacements, the user should never need these since they're
			// normal characters this prevents like
			// <IMG SRC=&#X40&#X61&#X76&#X61&#X73&#X63&#X72&#X69&#X70&#X74&#X3A&#X61&#X6C&#X65&#X72&#X74&#X28&#X27&#X58&#X53&#X53&#X27&#X29>
			// Calculate the search and replace patterns only once
			$search = 'abcdefghijklmnopqrstuvwxyz';
			$search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
			$search .= '1234567890!@#$%^&*()';
			$search .= '~`";:?+/={}[]-_|\'\\';
			for ($i = 0, $istrlen_search = strlen($search); $i < $istrlen_search; $i++) {
				// ;? matches the ;, which is optional
				// 0* matches any padded zeros, which are optional
				// &#x0040 @ search for the hex values
				$patterns[] = '/(&#x0*'.dechex(ord($search[$i])).';?)/i';
				$replacements[] = $search[$i];
				// &#00064 @ 0* matches padded zeros
				// with a ;
				$patterns[] = '/(&#0*'.ord($search[$i]).';?)/';
				$replacements[] = $search[$i];
			}
		}
		$val = preg_replace($patterns, $replacements, $val);
		if ($val_before == $val) {
			// no replacements were made, so exit the loop
			$found = false;
		}
		return $found;
	}

	function RemoveXSSregexp(&$ra, &$val, $prefix = '', $suffix = '', $allow_spaces = false)
	{
		$val_before = $val;
		$found = true;
		$patterns = array();
		$replacements = array();

		$pattern_sep = '('
			.'&#[xX]0{0,8}[9ab];?'
			.'|&#0{0,8}(9|10|13);?'
			.'|(?ms)(\/\*.*?\*\/|\<\!\-\-.*?\-\-\>)'
			.'|(\<\!\[CDATA\[|\]\]\>)'
			.'|\\\\?'
			.( $allow_spaces ? '|\s' : '' )
		.')*';

		$pattern_start = '/';
		if ( $prefix != '' ) {
			$pattern_start .= '(' . $prefix . '\s*' . $pattern_sep . ')';
		}

		$pattern_end = '/i';
		if ( $suffix != '' ) {
			if ( $suffix == '=' || $suffix == ':' ) {
				$replacement_end = $suffix;
				$pattern_end = '(' . $pattern_sep . '\s*' . $suffix . ')' . $pattern_end;
			} else {
				$replacement_end = '';
				$pattern_end = $suffix . $pattern_end;
			}
		} else {
			$replacement_end = '';
		}

		for ($i = 0, $isizeof_ra = count($ra); $i < $isizeof_ra; $i++) {
			$pattern = $pattern_start;
			for ($j = 0, $jstrlen_rai = strlen($ra[$i]); $j < $jstrlen_rai; $j++) {
				if ($j > 0) {
					$pattern .= $pattern_sep;
				}
				$pattern .= $ra[$i][$j];
			}
			$pattern .= $pattern_end;
			$replacement = ( $prefix != '' ) ? '\\1' : '';
			// add in <> to nerf the tag
			$replacement .= substr($ra[$i], 0, 2).'<x>'.substr($ra[$i], 2);
			$patterns[] = $pattern;
			$replacements[] = $replacement.$replacement_end;
		}
		// filter out the hex tags
		$val = preg_replace($patterns, $replacements, $val);

		if ($val === null) {
			Feedback::error(tr('Filter error: "%0"', 
				array_flip(get_defined_constants(true)['pcre'])[preg_last_error()]), 'session');
		}
		if ($val_before == $val) {
			// no replacements were made, so exit the loop
			$found = false;
		}

		return $found;
	}
}