Yahoo users who have received email messages like the one below, which claim that they need to upgrade to Yahoo Mail V 15.0.11 and threaten to close your accounts permanently if you do not are asked to delete them and should not follow the instructions in them. This is because the email messages are phishing scams being sent by cyber criminals to trick Yahoo users into clicking on the link in them, which goes to phishing websites that steal Yahoo usernames and passwords.
A Sample of the "Upgrade to Yahoo Mail V 15.0.11" Email Scam
On Mon, Jul 17, 2017 at 6:44 AM, Yahoo Mail
We notice your yahoo mail account has an Outdated status, Sign-in to upgrade your mailbox to V 15.0.11 and continue to enjoy Mail to avoid account closure.
Click the button below to Sign-in and upgrade to continue using this service
Yahoo users should never click on a link to sign into their accounts; they should instead, go directly to mail.yahoo.com or yahoo.com and sign-in from there. Once they are signed in, they will be alerted to updates, changes or other important notifications. Going directly to Yahoo’s website to sign into their accounts, will protect Yahoo users from phishing links that go to fake websites that steal usernames and passwords. Phishing websites steal their visitors’ usernames and passwords by asking them to sign into their accounts on the same fake website. Once visitors to the websites attempt to sign-in, their usernames and passwords (credentials) will be sent to the cybercriminals responsible for the phishing websites. As soon as the cyber criminals receive their potential victims’ usernames and passwords, they will sign into their accounts, hijack and use them fraudulently.
Yahoo users who have been tricked by the "Update to Yahoo Mail V 15.0.11" or "Upgrade to Yahoo Mail V 15.0.11" email scam, are asked to change their Yahoo passwords immediately before their accounts are hijacked and used fraudulently.