While working with ADFS claim aware site in SharePoint 2010, there is one issue regarding the sigout from the portal. Even if the user sign out from the portal, the cookie still persists and when user tries to login again he will be automatically signed in without prompted for re-authentication.
We can overcome this issue by implementing below steps :
1. Signout url -->
To correctly log out, we need to browse to the ADFS sign out url like
2. Setting the FedAuth cookie to be session based -->
In order to have correct sign out behaviour (even after setting the signout url as shown in step 1) we need to make the FedAuth cookies as session based. We can achieve this by running the following powershell command :
$sts = Get-SPSecurityTokenServiceConfig
$sts.UseSessionCookies = $true
The details for the FedAuth cookie behaviour can be found here
Hope this post will be helpful to resolve the sign out issue.