UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.94 Safari/537.36

Steps to reproduce the problem:
1. Create a webpage with an iframe and a mouseup event listener. 
The mouseup event listener has to listen to an element touching 0,0
2. The iframe webpage has a mousedown event listener which does two things:
   - It calls event.preventDefault() to stop the default action of the mousedown.
   - It creates a new window using window.open('SOME_URL');
3. Click inside of the iframe, opening the new window

What is the expected behavior?
The mouseup event does not fire.

What went wrong?
When the iframe creates this window in a new tab the parent page's mouseup event listener is fired.
That is the bug. Furthermore the mouseup event fires at 0,0

Did this work before? N/A 

Chrome version: 50.0.2661.94  Channel: n/a
OS Version: OS X 10.11.3
Flash Version: Shockwave Flash 21.0 r0

This behavior does not occur in Safari Version 9.1 (11601.5.17.1) or Firefox 37.0.2

I've included two webpages which reproduce the bug, one of them serving as an iframe to the other.
Try it out by opening test.html in chrome and clicking inside of the iframe to see the bug output in console.
 

Deleted: test.html 267 bytes

test.html 267 bytes View Download

Deleted: iframe.html 287 bytes

iframe.html 287 bytes View Download