Climbing the stairs

Dahlia loves climbing the stairs. If the gate is left open for 30 seconds, she speed crawls over to it and begins her ascent. One day, while I was tidying up where we were playing together, I followed her into the other room, and she...was...not...there...Out of the corner of my eye, I caught some movement and there she was, at the top of the stairs, *in* the kitty litter box on the landing. Bad mommy! I wasn't sure which was more dangerous--the awful disease she'd get from kitty poo or the broken neck she would have gotten from falling down the stairs. I don't usually forget to close the gate anymore! Fortunately all ended well!