Hi. Can someone please tell me how it is possible for someone who I am not friends with on CM to be..

Hi. Can someone please tell me how it is possible for someone who I am not friends with on CM to be able to attack me repeatedly? I have just had my village completely trashed by the same person who has attacked me over 20 times in the space of 1 hour. I have no idea who they are and CM will only allow me to revenge attack them back once. How can they be able to attack me so much. Any ideas please?