TDuck survey form through 6.0 Authorization Bypass via User-Controlled Form Key in POST /user/form/item/batch/create

TDuck survey form through 6.0 contains a broken access control vulnerability that allows authenticated users to add fields to other users' forms via POST /user/form/item/batch/create. Attackers can submit an array whose first element references their own form and later elements reference a victim's formKey, injecting attacker-chosen fields onto the victim's public fill page.