I run a small open-source multi-agent platform. A few months after launch, someone reached out with a responsible disclosure. It wasn't fun reading, but it was the most useful feedback I've gotten. Writing it up in case it saves someone else the same mistakes.

1. API keys reachable from the client

Keys were being handed to the browser. Anyone with devtools had them. Obvious in hindsight, easy to miss when you're moving fast and the thing "works."

Fix: all provider calls go through a server-side proxy. Nothing sensitive crosses the network boundary.

2. IDOR on resource endpoints

Endpoints checked that you were authenticated, not whether you owned the thing you asked for. Increment an ID, read someone else's data.

Fix: ownership check on every handler, not just auth.

3. Row Level Security never enabled

This is the Postgres/Supabase trap. You write your access rules in application code, they work, you ship. But anything hitting the DB directly bypasses all of it. RLS off means your policies are suggestions.

Fix: RLS on every table, deny by default, then open explicitly.

4. Predictable room codes

Short sequential-ish codes. Enumerable. You could walk the space and find live sessions.

Fix: cryptographically random, longer, plus rate limiting on lookup.

What I'd actually take away from this:

Three of the four came from the same root cause — trusting the client and treating auth as a single gate instead of a check at every boundary. If you're building anything multi-tenant, assume every ID is guessable and every client is hostile.

Also: publish a way for people to report this stuff. The only reason I found out was that someone bothered to write to me instead of just using it.

A security researcher found 4 vulnerabilities in my multi-agent platform. Here's the full breakdown.