Improper privilege management in WP Swings Subscriptions for WooCommerce

Summary

The Subscriptions for WooCommerce plugin for WordPress is vulnerable to Privilege Escalation in versions up to, and including, 2.0.0. This is due to the `save_meta_boxes()` function persisting the `_wps_plan_user_role` membership plan meta from `$_POST` without an allowlist that excludes privileged roles — the only validations applied, `sanitize_key()` and `wp_roles()->is_role()`, both accept `'administrator'` as a valid value, and the UI's `disabled` attribute on the role dropdown is a client-side-only control trivially bypassed via DevTools or a direct POST request; additionally, because the `wps_membership_plan` custom post type is registered with `capability_type => 'post'`, any user who can edit posts satisfies the `current_user_can('edit_post', $post_id)` guard in `save_meta_boxes()`. This makes it possible for authenticated attackers, with Contributor-level access and above, to escalate their privileges to Administrator by storing `'administrator'` as the role granted on membership acquisition, which the Pro companion plugin then applies via `add_role()` during membership lifecycle events. Successful exploitation requires the Subscriptions for WooCommerce Pro companion plugin to be active, as it is the component that reads the stored `_wps_plan_user_role` meta via `get_post_meta()` and calls `add_role()` to apply the role during membership lifecycle events.