调用接口：https://developers.weixin.qq.com/doc/offiaccount/Asset_Management/Getting_Permanent_Assets.html

返回值：

{"errcode":0,"errmsg":null,"title":"公众号后台上传的视频","description":"","downUrl":"http://mp.weixin.qq.com/mp/mp/video?__biz=MzU4NTg1NjMwNw==&xxxxxx","tags":[]}

有的时候是直接返回个可以下载的视频地址：

{"errcode":0,"errmsg":null,"title":"SampleVideo_1280x720_2mb.mp4","description":"","downUrl":"http://203.205.137.71/vweixinp.tc.qq.com/1007_de9e6431ee934509aab6edd76961f5dc.f10.mp4?xxxx","tags":[]}

不是应该返回视频的下载链接么？为了防止数据泄露改了后半部分参数，到底是为什么？？？