Arguably, it can make it less secure by reducing the user's control over what content the browser loads or what scripts it executes. For example, users may be using extensions to selectively replace harmful content (like intrusive JavaScript, tracking) with benign content. It is a balance between security for the user and security for the website owner.
> It is a balance between security for the user and security for the website owner.
Which in the case of browsers should always be decided for the user, rather than balanced. The browser is a user agent. It is running on the user's hardware.
Exactly. It's been clearly established that web extensions' code is more priveleged than a page code, as it should be. The amount of people going 'muh sesoority' in this thread is baffling.