Hmm, so I find an email in my junk folder purporting to be from Yahoo, titled 'Yahoo Security Breach Proposed Settlement', send to the old email address I used for Tumblr.
First red flag: my email address is a .uk one, but the settlement is only for US and Israeli citizens.
Suffice to say, the website linked to in the email was promptly blocked by my anti-virus.
It's a scam, probably to plant malware on your computer. Warn your friends and family.