Got this email today:
More info: https://support.apple.com/en-us/HT204915
We also need app specific password to upload app from Application Loader, more info: https://support.apple.com/en-us/HT204397
Dear xxxxx,
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
More info: https://support.apple.com/en-us/HT204915
We also need app specific password to upload app from Application Loader, more info: https://support.apple.com/en-us/HT204397