next-video: Unauthenticated arbitrary file read via /api/video request handler

Summary

next-video is a library for adding video to Next.js applications. Prior to 2.8.1, the GET endpoint exported by next-video/request-handler and commonly mounted at /api/video accepts an unauthenticated url query parameter, while src/utils/utils.ts isRemote() treats any value without an HTTP or HTTPS prefix as a local path. src/request-handler.ts passes that value through src/assets.ts getAssetPath() to src/config.ts loadAsset(), which appends a JSON suffix and uses fs.readFile without canonicalizing the path or verifying that it remains inside the configured video folder. A remote attacker can therefore escape the intended asset directory and read JSON files accessible to the application process, including Next.js server-action encryption material, preview-mode keys, build manifests, route metadata, absolute paths, and application video asset identifiers. Applications that do not expose the runtime request handler are not affected through this route. This issue is fixed in version 2.8.1.