See details from https://github.com/openshift/console/pull/12223:

subjectName can contain special characters like # which is a reserved character in a URI. This change URI encodes this parameter to avoid creating a broken link.

Before this change it was possible to create a group with a # in the name and click "Create binding" from the "RoleBindings" tab to create a broken view where the data is not correctly pre-filled.