BookStack before 26.09.3 contains a missing authorization vulnerability in ImageController:...

BookStack before 26.09.3 contains a missing authorization vulnerability in ImageController::checkImagePermission() that allows authenticated non-admin users to bypass page-level content restrictions for images whose owning page has been moved to the recycle bin, because the permission check relies on Page::getPage() which returns null for soft-deleted pages and silently skips the PageView check. Attackers can enumerate sequential image IDs via GET /images/edit/{id} to disclose metadata of restricted images, and users with image-update-all/image-delete-all privileges can rename, replace, or permanently delete images belonging to content they cannot view, persisting the damage even after the page is restored.