Open riser stairs with squeaky treads
You could try tighting the brackets. If the brackets are screwed on unscrew remove thread and apply some adhesive like F-26 or Liquid Nail then reinstall. If that's not possible you could screw or nail thru top of thread directly to the riser.  This old school trick might be an option, squirting a small amount of either baby powder or graphite between the tread and riser. I'm guessing the stairs are made of wood.