Today, Apple sent out an email to all members of its developer program, saying that they'll have to use two-factor authentication to access their account, and Certificates, Identifiers, & Profiles, beginning on February 27. The firm has been requiring this for new Apple Developer members for some time, but now it's finally going to be required for everyone.
Here's the full text of the email:
"In an effort to keep your account more secure, two-factor authentication will be required to sign in to your Apple Developer account and Certificates, Identifiers & Profiles starting February 27, 2019. This extra layer of security for your Apple ID helps ensure that you're the only person who can access your account. If you haven't already enabled two-factor authentication for your Apple ID, please learn more and update your security settings.
If you have any questions, contact us.Best regards,
Apple Developer Relations"