To reproduce this bug:

1. Open the attached project
2. Open scene 'Game Scene'
3. Build&play the scene on the WebPlayer
4. The collision objects that are assigned to the buttons stay detectable outside the masking area
5. Move the mouse just bellow the scrollable area and the WebPlayer
6. Notice that buttons interact with mouse even when they are bellow web player's playable space

Captured reproduction: http://screencast.com/t/yy7x7qSBguAO

We are removing support for the webplayer, so we won't be fixing this