I have the exact same problem, but I think there is some confusion here.
For me, these unwanted addresses are not from the contacts list, BUT,
as soon as you click the "To:" line and start to type in an address, hundreds
of addresses from spam and everything else previously sent to me pop up
in a box as choices in alphabetical order, along with contact list addresses.
(Previous versions of Yah Mail only showed addresses from the Contact List
when using the "To:" line.) You can X out these extra unwanted address
choices one at a time, but after 50 or so, I get tired and stop. This only occurs when I begin to type an address in the "To:" line. If I go to my Contacts List, these hundreds of unwanted addresses do not appear. I have found NO solution in the Settings Controls for this continuing problem and I hate it. PS. I pay for my Yahoo Email Acct and had it for years, but it's awful now and I may change it.....Hope someone has an answer for this.