[FD] Unvalidated Redirect in Shibboleth component of Blackboard Learn

[Ethan Sweet <ethan@xxxxxxxx>]

CVE-2017-18262



[Description]

Since at least the 17th of October 2017 (Initial report date) Blackboard Learn 
has allowed Unvalidated Redirects on any signed in user through its endpoints 
for handling Shibboleth logins.



The vulnerable endpoint is: 



BLACKBOARD/webapps/bb-auth-provider-shibboleth-BBLEARN/execute/shibbolethLogin?returnUrl=myEvilUrl&authProviderId=realAuthProvider



Where:

BLACKBOARD is the Blackboard Learn web server endpoint.

myEvilUrl is any URL you want, URL encoded of course.

realAuthProvider is the auth provider, normally you can just gather this by 
attempting a real shibboleth login and looking at what authProviderId is set to.



This attack only works against Blackboard Learn web servers with Shibboleth set 
up.



[Reproduction steps]



Set up a blackboard learn web server, make sure shibboleth is set up.

Copy the shibboleth login URL from the sign in page (should look like the 
endpoint above)

Replace the returnUrl with another URL (myEvilUrl).

Open the URL and log in as normal (if not already signed in properly to 
complete shibboleth login).

You will be redirected to the returnUrl you gave, regardless of what that url 
is.





[Type]

Unvalidated Redirect



[Vendor]

Blackboard Inc


[Discoverer]
Ethan Sweet



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