Scrolling a browser extension's popup window scrolls the main page

[tomayac]

Find an extension with a popup window that scrolls (I tried with the Cross-Origin Storage extension). Open the popup window and try scrolling. Observe how the main page scrolls instead of the popup window when you scroll with the mouse. (You can scroll by focusing the popup window and scrolling with the arrow keys.)

[velzie]

does setting GECKO_APZ=0 help? load with ?env.GECKO_APZ=0

[tomayac]

does setting GECKO_APZ=0 help? load with ?env.GECKO_APZ=0

No, this didn't make a difference, the underlying page still scrolls, not the extension popup window.

(Sorry for the long turn-around time, I was OoO without access to a desktop computer to test this.)