Mysterious crack on new macbook

I have had my mac book for just over 8 months now and a few days ago a small black crack appeared on the bottom left corner of my keyboard. I have not dropped or banged it and is a complete mystery. Is this covered by my apple care? i have heard stories about people just going and getting new cases for free is that true?

Hi i work for apple and this is a known issue and is covered under your warranty. you can take it to apple store, authorize repair center, or call 1-800-my-apple to setup a mail in repair.