It could be in result of an up and coming buy out ??
Ive never rated Yahoo personally but i say its as vulnerable as any other provider.
The Main thing to do if you have a Yahoo account is to update you passwords and security questions.
I would do it even if you're not on there list of compromised accounts.
This is the web.site to check whether youve been hacked or not. Says my accounts are ok but I don't know how reliable it is. Was given out by moneysavingexperthttps://haveibeenpwned.com/
It makes good reading, however i wouldnt want to enter my account details into a none yahoo site search at this time. I would just assume if your with Yahoo your details at the least need to be updated.
These guys wont be the last to fall victim. Cyber war is real, and the trophies are getting larger each time.