Before reporting an issue

[x] I have read and understood the above terms for submitting issues, and I understand that my issue may be closed without action if I do not follow them.

Area

admin/ui

Describe the bug

Hello,

Since the 26.4.0 update, I simply cannot add users anymore from the Admin UI.

Version

26.4.0

Regression

[x] The issue is a regression

Expected behavior

I should be able to reach the usual "add user admin UI" to create the user.

Actual behavior

I am getting the client error message can't access property "includes", u.value is undefined.

<img width="1916" height="223" alt="Image" src="https://github.com/user-attachments/assets/31b07e13-c472-4419-aa8f-de5c0812d70e" />

How to Reproduce?

I am using the admin account from the master realm, and I am trying to create an user in another realm.

The bug is triggered by opening this URL:

https://<keycloak_domain>/admin/master/console/#/<keycloak_realm>/users/add-user

The issue is triggered on both the base and the keycloak.v2 admin UI.

I am using the Docker version of Keycloak, the host is running Debian Trixie (stable), the following plugins are enabled:

• keycloak-bcrypt
• keycloak-altcha

The feature organization is enabled, though it is currently disabled for this realm.

There is nothing in server logs, this is likely an UI issue only.

Anything else?

I have another, empty test realm in which the bug does not happen. I suppose there must be specific conditions for this bug to trigger.
The UI always crashes on the affected realm.