Envira Gallery < 1.16.2 - Author+ Non-Public Post Title and Excerpt Disclosure via Gallery REST Field

The Envira Gallery WordPress plugin before 1.16.2 does not verify that an image identifier added to a gallery refers to a media attachment the caller is permitted to view, allowing any user able to create and edit a gallery (Author and above by default) to disclose the title and excerpt of other users' private, draft, pending and trashed posts that WordPress would otherwise withhold from them.