The short answer to this question is: definitely not! It is technically impossible.
The authentication using Yahoo means two things:
- the authentication process is fully delegated to Yahoo
- your Yahoo authentication is connected with a Teamness account (if exists, otherwise a new one can be created).
Or, to put it in different words, the following steps are performed:
- you are accessing the Teamness login page and click on the "Login using Yahoo" link
- you are redirected to the Yahoo login server along with a secret key
- you login on the Yahoo server and authorize Teamness to access your details
- you are redirected to the Teamness website along with another secret key generated by Yahoo from the one we’ve just sent
- the information received is validated by the Teamness server to make sure that you indeed logged in successfully on the Yahoo server and then your email address and full name are retrieved to connect you to your Teamness account
The entire authentication procedure is performed on the Yahoo servers and there are no passwords exchanged during this time. Only at the end of the process Yahoo is redirecting you on the Teamness site confirming that it was able to authenticate you. As you can see, obtaining someone’s password is impossible because the password is never sent out of the Yahoo servers.