New Yahoo security alert?

No. downrightnow.com and downdetector.com both confirm there's a problem with Yahoo.
Might be a server issue at your region, SEA region is perfectly fine for me, I just checked my mail and again I could access it. More specifically I'm accessing it through a Singapore server
 
Problem here in UK. Maybe it's just coincidence I got the LastPass alert whilst Yahoo was down. Could simply be a late response to the news released the other day about the 2014 breach. I guess we'll find out soon.

Or going by how long Yahoo took to let us know about the 2014 breach, maybe not so soon.
 
YAHOO is accessible in Germany at this time. Tonight i checked my Yahoo-Inbox. There was an eMail
from YAHOO with informations about the breach in 2014 and that i should change my password because my account could be affected.
I changed my password: everything seems to work fine ... no problems with YAHOO.

Yahoo Mail has been down for several hours and I'm now getting a message from LastPass saying there has been a major Yahoo security breach and I should change my password immediately.

..yes also saw this message from LastPass....