I not asking everyone to check their account. I saying if you do check your account do you get this message as well. Also, I have changed my password recently and I got these message.
Contrarily to what you might believe nothing is foolproof. Google doesn't have customer service for their free services for a reason. Change your password, use a password generator so it is complicated. If you are using chrome sync make sure to delete all add-ons and sync it. Celebrities get hacked because they are special. Friend you are SPECIAL!!
I not hacked. I waited about ten min. to sign out everyone. Then I sign back in with no changes happen to my account.
Hacked or not there is obviously an issue with your account. I believe "resetting" which can be done by changing your password is the best option.
I know I not everyone but I seen a post about someone that just making an account and it happen to them. I don't know if my case is different or it might just be google itself. I don't want to make another account to test it, if it has been done before.
It's possible for you to have connected via a different ip. From what I know, if you have a safety e-mail adress, then, google will send an e-mail to that e-mail adress in case that you'll change the device/ip adress.
Unless you explicitly sign out from a site, your session will remain valid until it expires. So, deleting your cookies was in fact the "problem". This happens with NU as well; they just don't tell you.