[Cpoll]

It's using window.screenY (and screenX, of course,) which gives absolute coordinates. https://developer.mozilla.org/en-US/docs/Web/API/Window/scre...

I don't think the method you're describing exists. If you want child coordinates relative to parent coordinates, you would use both the parent and child's absolute coordinates.

[sleepychu]

Thanks to you (and others who've provided this information), so I guess my question now is what is the privacy leak described. I understand that the browser is confessing information about the machine to the web page but I don't understand why that represents a private piece of information. I feel like the information about where the window is located on the screen is useful for implementation and I can't think what it says about me as a user.

[nommm-nommm]

Nothing on its own. However it is one of the pieces of information used to create a unique fingerprint for your browser which can be used to track you as you travel across the web. IIRC Tor browser recommends never resizing the window from the browser's default window size.

[softawre]

https://github.com/Valve/fingerprintjs2