Please do not file public GitHub issues for security vulnerabilities.

Instead, email the repository owner with:

• A description of the issue
• Steps to reproduce
• Impact assessment (if known)

We will acknowledge receipt and work on a fix as soon as possible.

• Never commit .env, session cookies, or API keys.
• Set API_SECRET on all production / Vercel deployments — tool routes are disabled without it in production.
• Treat Substack connect.sid values like passwords; rotate them if exposed.
• Runtime comment history is stored locally in src/data/comments_history.json and is gitignored — do not commit it.

The web dashboard at /playground persists the following in browser localStorage:

• Substack connect.sid session cookie and publication URL (substack_settings)
• AI provider API keys per provider (substack_apikey_*)
• Theme, sidebar state, and system prompt preferences

Treat these values like passwords. Anyone with access to your browser profile can read them. Clear site data or disconnect when using a shared machine.

When you click Connect, your session cookie is sent to your running Substack Agent server (POST /api/connect). The server uses it to call Substack on your behalf. It is not sent to third parties, but it does leave the browser.

The dashboard API is designed for local development (npm run dev). If you deploy the playground publicly with SUBSTACK_SID in server environment variables, anyone who can reach your deployment can control your Substack account via unauthenticated dashboard routes. Use tools API auth for production integrations instead.

• /api/tools/* endpoints require Bearer auth when API_SECRET is set. In local development only, auth is skipped when API_SECRET is unset.
• On Vercel, scheduler and history data may be stored in ephemeral /tmp and lost on cold starts — use local npm run dev for reliable scheduling.