CVE-2026-53658: Fabric CA Developer's Guide: LDAP Injection via Unescaped Username in GetUser Filter

When fabric-ca is configured with an LDAP backend, the username from HTTP Basic authentication is included in an LDAP uid search filter without proper escaping. An unauthenticated attacker with network access to the CA enrollment endpoint could exploit this to perform LDAP injection before password validation, and potentially steer authentication attempts toward a victim account.