Cmseasy latest version of stored XSS (xss protection mechanism can be bypassed) #2
Html is a very interesting language ..
The xss code in the bbs posting area of cmseasy performs a complete filtering of the html code in <>.
function xss_clean($data) { if (empty($data)) { return $data; } if (is_array($data)) { foreach ($data as $key => $value) { $data[xss_clean($key)] = xss_clean($value); } return $data; } $data = str_replace(array('&', '<', '>'), array('&amp;', '&lt;', '&gt;'), $data); $data = preg_replace('/(&#*\w+)[\x00-\x20]+;/', '$1;', $data); $data = preg_replace('/(&#x*[0-9A-F]+);*/i', '$1;', $data); if (function_exists("html_entity_decode")) { $data = html_entity_decode($data); } else { $trans_tbl = get_html_translation_table(HTML_ENTITIES); $trans_tbl = array_flip($trans_tbl); $data = strtr($data, $trans_tbl); } $data = preg_replace('#(<[^>]+?[\x00-\x20"\'])(?:on|xmlns)[^>]*+>#i', '$1>', $data); $data = preg_replace('#([a-z]*)[\x00-\x20]*=[\x00-\x20]*([`\'"]*)[\x00-\x20]*j[\x00-\x20]*a[\x00-\x20]*v[\x00-\x20]*a[\x00-\x20]*s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:#i', '$1=$2nojavascript...', $data); $data = preg_replace('#([a-z]*)[\x00-\x20]*=([\'"]*)[\x00-\x20]*v[\x00-\x20]*b[\x00-\x20]*s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:#i', '$1=$2novbscript...', $data); $data = preg_replace('#([a-z]*)[\x00-\x20]*=([\'"]*)[\x00-\x20]*-moz-binding[\x00-\x20]*:#', '$1=$2nomozbinding...', $data); $data = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?expression[\x00-\x20]*\([^>]*+>#i', '$1>', $data); $data = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?behaviour[\x00-\x20]*\([^>]*+>#i', '$1>', $data); $data = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:*[^>]*+>#i', '$1>', $data); $data = preg_replace('#</*\w+:\w[^>]*+>#i', '', $data); do { // Remove really unwanted tags $old_data = $data; $data = preg_replace('#</*(?:applet|b(?:ase|gsound|link)|embed|frame(?:set)?|i(?:frame|layer)|l(?:ayer|ink)|meta|object|s(?:cript|tyle)|title|xml)[^>]*+>#i', '', $data); } while ($old_data !== $data); return $data;}
However, do we really need to <>?
In a test, will the following code be alert?
<body>
Once you run the command, you will find alert. Because . Cause js execution
The above example will soon get another xss Code .
Filter
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