Login to Blackboard Learn as administrator

Configure a SAML authentication provider using IdP metadata that contains only HTTP-Redirect as the SingleSignOnService binding

Open the browser Developer Tools, select Network, and enable Preserve log

Sign out of Blackboard Learn

Start the SAML SSO login from the Blackboard Learn sign-in page

Locate the request sent from Blackboard Learn to the IdP

Verify the request method:

Affected build: Blackboard Learn sends the SAML AuthnRequest using POST, and the login fails.

Fixed build: Blackboard Learn sends the request using GET/Redirect, and the login succeeds.

Inspect the decoded SAML AuthnRequest

Do not use the ProtocolBinding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST" attribute to determine the outbound request method. This attribute tells the IdP how to return the SAML response to Blackboard Learn, so seeing HTTP-POST here is expected

Repeat the test with the following IdP metadata combinations:

HTTP-POST only: Request should use POST

HTTP-Redirect only: Request should use GET

Redirect listed before POST: Request should use GET

POST listed before Redirect: Request should use POST

Confirm that the fixed build uses the first supported binding listed in the IdP metadata, while the affected build always uses POST. These are the comparison conditions documented in Bug 701684 SAML SSO Login Issue – Blackboard SP Sending POST Request Instead of GET