Captive Portal account limitation with Nebula

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Case Study: Captive Portal Authentication Limitation with Nebula

A customer asked Why does Nebula authentication fail when the user account format starts with a special character # ?

In this case, the authentication process ends before the RADIUS Access-Request is generated.

The customer’s HAR confirmed that the authentication request is already submitted by POST and the username is correctly included in the request body. Therefore, the issue is not caused by browser URL redirection or GET parameter truncation.

In many captive portal authentication designs, usernames that start with special characters may be restricted or handled differently to avoid parsing, validation, or authentication flow issues.

This case has been identified as a current Nebula AP processing limitation. The behavior design consideration where leading special characters are not treated as standard account identifiers in the authentication handling flow. Therefore, for the current Nebula AP implementation, usernames should begin with an alphanumeric character, while special characters may be used later in the username if required.

This case will be converted into a feature request across multiple AP authentication handling layers.