Web Request: Explaining the Impact on Extensions in Manifest V3

With Web Request, Chrome sends all the data in a network request to the listening extension – including any sensitive data contained in that request like personal photos or emails. As a result, extensions that leverage the Web Request API typically have access to read and manipulate everything a user does on the web. Because all of the request data is exposed to the extension, it makes it very easy for a malicious developer to abuse that access to a user’s credentials, accounts, or personal information.

Source: blog.chromium.org