Bug: Selecting text in overlapping iframes

Observed in MobileSafari for iOS versions 3.1 — 4.1.

Description of bug: Both boxes below display two iframes stacked on top of each other. Selecting text in the left box will actually select from the iframe underneath.

In the box on the left, the natural z-order is unchanged. The first iframe is underneath, the second is on top. This is the box that exhibits the bug.

In the box on the right, the z order has been reversed, so that the first iframe is raised to the top and the second iframe goes underneath. Text selection in this box behaves as expected.