I've get a fresh install of Kubuntu 17.10, and got KWallet asking me for password which I'd never set one more time. As far as I'm aware of - the same was with 17.04, 16.10, 16.04 and before. What I do every time to save my time - I just set it BLANK which seems like a mockery on common sense - you have your secure wallet open for everyone. This time I decided to create a bug report here because I want to understand so what the heck is wrong with either KDE or Kubuntu so that every time a new system is installed it just doesn't work after the first login and why on earth it's considered normal? Haven't I already setup my password when installed the system? I have. Haven't I had working browser in the first session? I have. So why can't KWallet just unlock itself if I start MY session with MY password?
You need to install and setup pam-kwallet, if you have configured KWallet with the same password as your login, and automatically want the wallet to unlock. Please ask in a forum of your distribution how to use pam-kwallet. See also https://www.dennogumi.org/2014/04/unlocking-kwallet-with-pam/