Second verification in the Yahoo is required to make your Yahoo account more secure. In this situation, you need how to contact yahoo for solving such problem.
But there is nothing to worry!
Here are some steps that help you know where the necessity of the second verification in your account is.
· Any suspicious activity in Yahoo
· Accessing your Yahoo account on unfamiliar browser
· Location changes from usual location
· Sign in while using any VPN or proxy server
· Using a private or incognito window to log in Yahoo mail
· Used many attempts to sign in with incorrect password
· First time sign in message appear while sign in
· Cleared the browser history or cache data including cookies.
These are some conditions where you will need to provide second verification to secure your Yahoo account.
More recommended: Guidelines how to contact Yahoo for the CAPTCHA verification problems