Because the percent sign (%) itself can be URL encoded, an attacker can submit a carefully crafted request to a server that is basically double-encoded.

由于百分号(%)本身可以是URL编码的，所以攻击者可以向服务器提交一个精心制作的、基本上是双重编码的请求。

youdao

Double spending and (probably short-duration) expiration checks further assure sincere interest in the edit. It was not difficult for me to generate the above URL using the command.

double spending和(可能持续时间较短)过期校验进一步为真正要进行编辑的行为提供了保证。

youdao

The company warned users to double-check the URL to ensure they were visiting the correct site.

CNN: Facebook, Twitter crooks just a click away