Yahoo Mail

https://mail.yahoo.com/
Recommended Configuration Proprietary; Email; SMS
Alternate Configuration 1 Email; SMS
Alternate Configuration 2
Alternate Configuration 3
Account/Password Recovery PR SMS; PR email
Remarks automatic SMS backup signup using phone number on file; automatic email backup signup using email on file; 1-step login (via notification, OTP via SMS, OTP via email) enabled if proprietary app 2FA is selected
Responses

Notified on January 11, 2020.

Closed on January 12, 2020; did not understand vulnerability with authentication policy.
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2fa_backup_step0.PNG
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2fa_backup_step1.PNG
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2fa_backup_step3.PNG
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2fa_backup_step4.PNG
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2fa_backup_step5.PNG
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2fa_options.PNG
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2fa_proprietary_step1.PNG
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2fa_proprietary_step2.PNG
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pr_juxtaposed.png
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pr_step0.PNG
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pr_step1.PNG
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pr_step2.PNG
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pr_step3.PNG