Please report suspected vulnerabilities through GitHub private vulnerability reporting. Do not open a public issue for an unpatched vulnerability. Include the affected version, reproduction steps, impact, and any suggested mitigation.

This experimental project does not currently publish a fixed response SLA. Reports will be acknowledged and triaged as maintainer capacity permits.

Each canvas instance starts an HTTP server on an ephemeral port bound only to 127.0.0.1 and creates a 256-bit random capability. All page, API, and SSE requests require that capability. Requests must also use the exact 127.0.0.1:<port> Host and either omit Origin or send the exact loopback origin. Mutations require application/json. Do not expose or proxy the bridge to another interface, publish its capability, or place the capability in logs.

The iframe receives a nonce-based Content Security Policy that blocks external scripts, fonts, media, objects, workers, and network connections. The runtime has no external CDN, telemetry, upload, or analytics dependency.

JSON request bodies are limited to 1 MB. Stroke, point, coefficient, layer, and keyframe counts, aggregate scene complexity, transform work, storage size, and numeric magnitudes are bounded before expensive processing or persistence. Persisted JSON uses atomic replacement, per-workspace mutation serialization, and revision checks for compositions. It is written only below the active Copilot workspace's fourier-assets/ and fourier-compositions/ directories. Invalid asset files are quarantined and reported through /api/info rather than preventing the remaining library from loading.

The extension requires no API keys or application credentials. Never add secrets to source, examples, screenshots, fixtures, or bug reports. Generated assets may still reveal the shapes a user created and should be handled as workspace data.

Security fixes are applied to the latest release. This repository is currently pre-release software without long-term support branches.