Has GUI mouse event handling changed in Unity 4.5?

My project has multiple in-world clickable objects (using trigger colliders and the OnMouseDown event). There are also various GUI menus and buttons created in OnGUI().

Using the previous version of Unity (4.3.4), clicking a GUI button would block the click event from going through to any world objects, which is correct.

If I run the project in the newly released Unity 4.5, it seems like mouse events are passed straight through GUI elements. So if the player selects something in their inventory, they also suddenly find themselves walking halfway across the level because that bit of ground happened to behind their inventory when they clicked.

I've prepared a tiny demo Unity project with a single world object and a single UnityGUI button to demo the issue.

You can download the project and run the scene with the console visible and try clicking on the sphere and the huge button. If you're running 4.3.4 (or less, I haven't tried yet) you'll see that clicking where the button overlaps the sphere causes just the button to activate. Upgrade to 4.5 and suddenly clicking the same place causes the button and the sphere to activate.