2 Factor Authentication enabled itself
If you plan to use an authenticator in the future, save its secret key. The key can be used to duplicate the authenticator whenever you want.
Devices are remembered based on your public IP address. Depending on your ISP, it may change regularly or remain the same.
I doubt an authenticator added itself. Assume your account has been compromised.
2 Factor Authentication enabled itself
in Account & Technical Support
Posted by: Inculpatus cedo.9234
You can, again, contact the CS Team via the ‘Support’ link above/below and ‘Submit a Request’ for assistance. (You might ask them to check for unauthorized use, as someone else may have installed the Authenticator.)
Good luck.
2 factor authentication doesn’t usually just turn itself on. You may want to check your recent logins. Someone may of accessed your account and added it to block you.