CVE-2026-55596: Plate: Media embed provider metadata can bypass URL sanitization and execute iframe JavaScript

The media embed renderer trusts serialized provider or sourceUrl metadata and skips the URL protocol validation that normally blocks unsafe media embed URLs. A crafted Plate document can set a known video provider while keeping url as a javascript: iframe source. When a victim opens that document in an app using the registry media embed component, the component renders the attacker URL directly as an iframe src.