Unfortunately, wildcard domains cannot use extended validation, per the CA/Browser Forum’s guidelines for Extended Validation (EV) certificates. The same guidelines require that each item contained in an EV certificate be individually vetted, which requires a unique identifier for each item. If you’re looking for extended validation for multiple subdomains, an EV UCC certificate may be the best option. An EV UCC allows for up to 500 entries (first three are included in the base price).