On Rialto, Sombra can use transponder to go inside of the payload. We just played a game against a team where the enemy Sombra did this on offense AND defense.
She can’t be hit by anyone or anything, trust me, our team tried. And she can still shoot/hack people outside of it.
Afterwards me and my friends made a custom game and it took about 30 seconds for us to figure out how to do it. I have a picture on my phone to show what it looks like, I don’t want to describe how to do it in case of copycats.