CVE-2026-62263: OpenAM: WebAuthn Java deserialization RCE via ObjectInputFilter depth>1 bypass

The GHSA-6c99-87fr-6q7r fix wrapped WebAuthn authenticator deserialization in an ObjectInputFilter meant to allow only AuthenticatorImpl, but it short-circuits to ALLOWED for any object at stream depth > 1. Because the Java serialization filter is consulted for every class in the graph (and depth == 1 only for the root’s concrete class), the allowlist constrains only the root and leaves the entire nested graph unchecked.