Signing Me onto Your Accounts through Facebook and Google: a Traffic-Guided Security Study of Commercially Deployed Sign-Sign-On Web Services. This is the whitepaper where researchers discovered eight flaws with SSO technologies in use by major players.
You can download it from the following link: https://packetstormsecurity.com/files/download/110998/websso-final.pdf
Source: https://packetstormsecurity.com/files/110998/Signing-Me-Onto-Your-Accounts-Through-Facebook-And-Google.html