Open Script Editor is a local, single-user app. Its API has no login and can read media files from your disk, so it is built to be reachable only from your own machine.

• Loopback only. The server binds to 127.0.0.1. Don't set HOST=0.0.0.0 or put it behind a public proxy.
• DNS-rebinding guard. Requests whose Host header isn't localhost, 127.0.0.1 or [::1] get a 403.
• Cross-site guard. Write requests that carry a non-local Origin get a 403, so a web page you visit can't drive the editor.
• Input validation.
  • Project and file ids are checked against a strict pattern.
  • Uploaded file names are reduced to a safe basename.
  • Import-from-path only accepts existing audio, video and image files.
  • Layer styles are coerced to bounded numbers before they reach ffmpeg or the SVG title renderer.
• No shell. ffmpeg and whisper-cli run with argument arrays, never through a shell.
• No telemetry, no cloud. Transcription (whisper.cpp) and rendering (ffmpeg) run locally. Nothing is uploaded anywhere.
• No secrets. The app needs no API keys. Keep any future keys in environment variables; .env* is git-ignored.

Please report it privately through GitHub → Security → Report a vulnerability on this repository rather than in a public issue. We'll acknowledge it within a few days.