If you have it set to automatically accept then there’s not much the sender can do since Apple Cash is tied to a debit card. Also, there’s usually a warning or notification prior to sending an unknown contact money basically stating once you send it then there’s no take backs.
There’s a lot of scams that sort of do this. A random number sends you Apple Cash tied to a fake account or the text gives you the illusion they sent something. The hope is you feel bad and send the “money” back before trying to move it to your bank but obviously you’re now sending real money.