"Will I be punished for any cheating or fraud conducted by other users while playing my games?
Your Family Library Sharing privileges may be revoked and your account may also be VAC banned if your library is used by others to conduct cheating or fraud. Additionally, VAC-banned games cannot be shared. We recommend you only authorize familiar computers you know to be secure. And as always, never give your password to anyone."

https://psteamproxy.yuanyoumao.com/promotion/familysharing
Be careful who you share your games with, don't let the same thing happen to you.