X-Powered-Byis part of an HTTP response header that indicates the technology or framework that generated the response. For example, if a website is written in PHP, X-Powered-Bythe field might be set to PHP/7.2.1. This gives us a clue as to which version of PHP is running.
Although X-Powered-Bythe information may have some reference value for developers or testers, this field is usually removed in production environments because it may expose too much system information to potential attackers. If an attacker knows that you are using a particular version of PHP or other technologies, they may be able to exploit known vulnerabilities in that version.
In practice, you'll likely see a variety of X-Powered-Bygimmicks. Here are some examples:
X-Powered-By: PHP/7.2.1X-Powered-By: ExpressX-Powered-By: ASP.NET
These headers indicate the technology used by the server generating the response. In the first example, the server is using PHP 7.2.1. In the second example, the server is using Express, a Node.js web application framework. In the third example, the server is using ASP.NET, a Microsoft technology for building web applications.
While X-Powered-Byheaders may be useful in some cases, in many cases they are not needed. This is because they may provide an attacker with useful information that does not actually need to be made public. For example, if you know your server has a specific vulnerability, you probably don't want to tell the world that you're using that version of the server software.
Therefore, many developers and organizations choose to remove or modify these headers. For example, you can configure your server to send a fake X-Powered-Byheader to confuse an attacker. Alternatively, you can remove the header entirely so the attacker doesn't have any clue as to what technique you're using.
In general, X-Powered-Byan HTTP response header that indicates the technique used to generate the response. While it may be useful in some cases, in many cases it is better to remove or modify this header to prevent providing useful information to an attacker.