What sits between a browser and an internet connection and alters requests and responses in...

An intercept proxy, also known as a proxy server, sits between a web client (such as a browser) and an external server to filter, monitor, or manipulate the requests and responses passing through it. This can be used for legitimate purposes, such as security testing and user privacy, but it can also be exploited by attackers to alter web traffic in a way that the developer did not intend, potentially leading to security vulnerabilities.

References:

Understanding of HTTP and HTTPS protocols12.

Definition and role of proxy servers3.