UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.84 Safari/537.36

Steps to reproduce the problem:
1. Open a text editor.
2. Move the Chromium window over the text editor window.
3. Select and drag text in Chromium
4. Drop it anywhere that the Chromium window overlaps the text editor window

What is the expected behavior?
The selected text is dropped into Chromium.

What went wrong?
The selected text is dropped into the text editor behind Chromium.

Did this work before? No 

Chrome version: 51.0.2704.84  Channel: n/a
OS Version: Arch
Flash Version: Shockwave Flash 14.0 r0

I've had this problem for years and finally just figured out that Chromium was the culprit. Sometimes, I'll focus an instant-messenger window or a text editor window from behind Chromium and find that seemingly random (but familiar) bits of text are scattered about in them, and I didn't know why. Now I see that they represent times that I accidentally clicked-and-dragged text in Chromium, and then dropped it in a place that seemed safe -- but it was actually dropping through the Chromium window and into the window behind it.

I run Arch Linux and Fluxbox is my window manager. Only Chromium is suffering this problem.

When there are no windows open behind Chromium, dragged items are dropped into Chromium normally, so it's as though, for the sake of a drag-and-drop operation, the Chromium window effectively drops to the bottom of all other windows, despite visually still appearing over them.