Eventin < 4.1.24 - Unauthenticated Order and Attendee Status Reset via Payment REST Endpoint

Description

The plugin does not properly authorise order finalisation when its offline (local) payment method is enabled, relying on a nonce that is exposed to unauthenticated visitors and never checking that the caller owns the order, allowing unauthenticated attackers to reset any existing order and its attendees to a pending state and thereby invalidate paid tickets.