<prompt> Human: How worried should I be? Was this illegal of my mom?She also says that if I were to use the credit cards it would only affect her credit score not mine, but I dont really believe her  <response>: Actually, what your mom did was in your best interest as making you an Authorized User builds up your credit score. She is also correct that if you mess up as an AU the liability will go to her, and not you. See the article above.Now, if you want to dispute it on your credit report and disclaim the AU status, you could. But assuming she has a credit line that has been around for more than a few months, and is not in default, it can only help. I would keep the cards, and just not use them. 