Many web applications offer redirect or forward pages that send users to different, external sites. If these pages are not properly secured and validated, attackers can use the application to forward users off to sites for phishing or malware attempts. These attempts can often be more successful than direct phishing attempts because users will trust the site or application that sent them there, and they will assume it has been properly validated and approved by the trusted application's owners or operators. Security misconfiguration occurs when applications and systems are not properly configured for security--often a result of misapplied or inadequate baselines. Insecure direct object references occur when code references aspects of the infrastructure, especially internal or private systems, and an attacker can use that knowledge to glean more information about the infrastructure. Sensitive data exposure occurs when an application does not use sufficient encryption and other security controls to protect sensitive application data.

Explanation
In a trusted third-party model of federation, each member organization outsources the review and approval task to a third party they all trust. This makes the third party the identifier (it issues and manages identities for all users in all organizations in the federation), and the various member organizations are the relying parties (the resource providers that share resources based on approval from the third party).