New member activated automatically?

Hi, I came home today to discover a new member on my forum. I have it set so that all new members must be activated by Admin. I checked the security admin actions log and there is nothing showing. The last member I activated was early November. How is it possible for someone to activate an account without Admin authorization? I dont want this to keep happening.

My forum is quilterslastresort.com

Thanks for your help

hello

he/she can if he/she used topic'it
you can create a group where members using topic'It will be automatically added to that group

I wasnt aware of this, how do I stop it, deactivate it on the forum?

thanks for helping

as far as i know yes if you deactivate this will solve the issue

Thank you, I will deactivate all of it, I dont use phones or tablets so was unaware of this kind of option appearing on the forums. I appreciate your assistance. Now I can go to bed and sleep without it driving me nuts wondering how it occurred.

you welcome 
if there is another solution i will tag @APE or @SLGray to help you

can we consider this topic solved ?

Yes thank you very much, I appreciate the quick response and help. Hopefully no one can slip on the forum anymore of their own accord.