How do I add someone on my online list on yahoo?

How is it possible for someone to add themselves to my Yahoo contact list?

• I was chatting with my SIL via Yahoo Messenger the other night. Suddenly another message box opened from someone I did not know. Username was not familiar at all. Also at the same time, the message box I was using with my SIL froze up, she kept typing to me, but I could not get any input into her message box to reply, even after I closed the box from the unknown user. The keyboard was functional under other programs, just not Messenger. A moment later a 2nd message box from same unknown user popped up. I closed it immediately as well. Hopped over to my contact list, and this username was at the very bottom of my contact list. I deleted the contact name, rebooted my computer, and everything seemed fine. I thought a request had to be made to be added. Can anybody explain what may have happened?

• Answer:

  yeah it is. if your not online they can add you. but theirs a pending request.