We are experiencing an exploit on free gifts. The coupon is working correctly until checkout, the user is able to add as many free gifts as they want.. Is there a way to limit it based on how many items are added to cart (based on product category?)
By default the free product quantity should be read only. Possibly your theme or a plugin overrides this. Do you have a plugin enabled that affects the ‘up/down’-checkboxes of the cart/checkout?
Can you please send me your WC System Status Report?