Pro life tip:

When they put the sticker on, immediately peel it off at the corner about halfway. Leave it like that.

Pass through security/passport control.

Once you're done with that, peel the sticker all the way off and stick it back-assedly onto your boarding pass, or your e-ticket printout, or whatever. It won't leave any residue on your passport if it's only on for a short time.

Go to gate, board plane as normal.

I'm really anal, and I hate those little stickers. I always remove them immediately. In 20+ years of international travel, I've never had anyone ever question me about this. But on the off chance that someone does, you can just say it must not have been fastened correctly and it attached itself to the other thing instead.