browsers implement cross domain origin policy to prevent js from accessing the local filesystem. Or did I misunderstand the nature of the Windows bug. It must be trying to read from file:// right?

Resources/frames/XHRs/etc from 'file://' might be blocked, but what about top-level redirects?

At the very least, user-initiated top-level navigations should bypass any policies. If you're out to cause mischief, you could just link to the dodgy path on forums/comments/etc – there'll always be people out there who are careless and/or clueless enough to click on it.

<img src="c://badfilename"> is enough. You don't need JavaScript.

But you do need the file to be stored locally. I don't think this attack is very serious. Downloading and opening files is already a risky maneuver.

My understanding of the article is there isn't a "local file" that matches the name, but the very act of checking for that filename causes the hang.

Happy to be corrected.

is this true for even evergreen browsers? Is this true for pages that's hosted in non localhost domain or drag n' dropped into browser from the file explorer? (file:// protocol)

heaven praise the same origin policy