and the reason for it is probably because you used either the same username or the same Email address for multiple places.
C-cex.com uses username, and for example if you had the name "Slow death" or chat there and show your username, someone can go to their login page and put in "Slow death" and try different passwords "123", "password1",... and every time he fails (assuming your password is not that easy to guess!) the system sends you an email telling you someone has failed to login.
This is the problem, my account from one of the sites has been hacked , I am watching now and I have already sent an email to block my account from this site.
Frankly, I did not receive email that someone changed the password.
beaware man those are russia hacker that try to hack your account of those exchange, i had the same thing from an unknown ip that tried to log in my hashnest account, but failed, those notification are useful, you can do a report to c-cex support and tell them that someone else was trying to login to your account, and they should unlock your account