Is not the first time than i receive an email of this type from xda and it's just to inform you or another user here
Someone has tried to log into your account on xda-developers with an incorrect password at least 5 times. This person has been prevented from attempting to login to your account for the next 15 minutes.
The person trying to log into your account had the following IP address: 18.104.22.168
All the best,