TLDR: DONT BE STUPID
Change your password
Change that password everywhere else you used it
Read this if you don't want to take my word for it:
http://www.nytimes.com/2016/09/23/technology/yahoo-hackers.html?_r=0
In fact, turn on two-factor authentication anywhere it's offered.
https://help.yahoo.com/kb/SLN5013.html
Don't sleep on this nonsense, change your damn passwords.
Change your password
Change that password everywhere else you used it
Read this if you don't want to take my word for it:
http://www.nytimes.com/2016/09/23/technology/yahoo-hackers.html?_r=0
In fact, turn on two-factor authentication anywhere it's offered.
https://help.yahoo.com/kb/SLN5013.html
Don't sleep on this nonsense, change your damn passwords.