Thanks OSUblake for the quick response!
Took me a while to track down the problem. Here is my forked version of yours.
No changes to your code, the only thing I added is the CSSPlugin.min.js in the setting. I use this plugin somewhere else in my application so leaving it out is not an option. Once this plugin is added, the hitTest() detection stop working in Firefox, no such problem in Mac Safari and Chrome with or without this plugin.