Improper signature verification in ThemeHigh Payment Gateway of Stripe for WooCommerce

Summary

The Payment Gateway of Stripe for WooCommerce plugin for WordPress is vulnerable to Improper Verification of Cryptographic Signature in all versions up to, and including, 5.0.8. This is due to the publicly accessible `woocommerce_api_wt_stripe` webhook endpoint (`EH_Stripe_Webhook_Handler::handle()`) wrapping the only call to `\Stripe\Webhook::constructEvent()` inside an `if (!empty($endpoint_secret))` guard that is never entered on default installations — because the `eh_stripe_webhook_secret` option is empty after a fresh plugin install — causing the raw, attacker-controlled POST body to be decoded and processed as a fully trusted Stripe event without any signature verification, authentication, or authorization. This makes it possible for unauthenticated attackers to send forged Stripe webhook events to manipulate WooCommerce order statuses, including marking unpaid orders as paid or completed via `payment_complete()`, forcing legitimate orders into a failed state, fabricating dispute notifications, and injecting forged refund events. This vulnerability is only exploitable when the Stripe webhook signing secret has not been configured by an administrator; once a valid signing secret is saved, `\Stripe\Webhook::constructEvent()` is enforced and forged requests are rejected.