What is the Infinity Effect?
When you're sharing your entire screen, and the screen that you are sharing is visible while on live video you get an effect similar to two mirrors reflecting each other. It creates what is known as an "infinite reflection effect" that looks like this:

This happens with any software that lets you see the screen share while you share your entire screen, even with Session.
Don't worry - it's not a bug and nothing's broken. 😀
How to Handle The Infinity Effect
To avoid the infinity effect, we recommend sharing a specific tab or window instead of your entire screen. If you have more than one monitor, another option is to share one screen and keep your Session window on the other.