Though each flaw had its own unique characteristics, all eight detailed in the report (PDF) had one trait in common.
"All these flaws allow the attacker to sign in as the victim to her accounts on the websites using SSO services even without knowing the victim's password," said Dr. XiaoFeng Wang, associate professor of computer science at Indiana University at Bloomington and co-author of the report with Rui Wang and Shuo Chen.
Wang and his team hope the report is a wake-up call for both the developers of websites using the SSO services and those providing the services, between whom there seems to be a disconnect as to who is responsible for hardening the SSO application. Further obscuring the matter is the fact that the SSO is going through browsers, whose behaviors are very complicated, Wang says.
"IT decision-makers should realize the security risk that comes with the convenience of SSO. Most problems we discovered actually can be fixed through correct integration on the website part. In other words, if the developer of these websites incorporate such SSO services carefully, SSO can be more secure," Wang says. "To make this happen, however, we also expect the help from the service provider side. They need to offer good integration supports, including well-specified documentation, verified secure code template, and other [support] to guide their customers during the integration process, which according to our findings, is very easy to get wrong."
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