Statamic: Incorrect authorization lets view-only users submit Live Preview content reserved for editors

Statamic is a Laravel and Git powered content management system (CMS). Prior to 5.74.0 and 6.20.3, the Live Preview endpoint for existing entries and terms in src/Http/Controllers/CP/PreviewController.php only checked view authorization, but it accepts and renders caller-supplied field values. A Control Panel user with view but not edit permission could therefore submit content they were not authorized to author and generate a shareable Live Preview URL rendering it. This issue is fixed in versions 5.74.0 and 6.20.3.