Common Issues auth

Users Can See Each Other's Private Data

Users in your app can see data that belongs to other users — viewing other people's orders, messages, personal information, or account details. This is a serious privacy and security issue that needs to be fixed immediately.

Common Causes

  • No Row Level Security (RLS) — database queries return all data, not just the current user's
  • API endpoints don't filter data by the authenticated user's ID
  • User ID taken from the request body instead of the authenticated session
  • Shared cache serving one user's data to another
  • Query fetches all records and filters on the frontend only

How to Fix It

  1. This is urgent — fix it before anything else. Consider taking the affected features offline temporarily.
  2. Check every API endpoint that returns user data — make sure it filters by the authenticated user's ID
  3. If using Supabase, implement RLS policies on all tables containing user data
  4. Never trust user ID from the request body — always get it from the server-side session
  5. Test by logging in as different users and verifying each only sees their own data

Real developers can help you.

Rudra Bhikadiya Rudra Bhikadiya I build and fix web apps across Next.js, Node.js, and DBs. Comfortable jumping into messy code, broken APIs, and mysterious bugs. If your project works in theory but not in reality, I help close that gap. Victor Denisov Victor Denisov Developer Jared Hasson Jared Hasson Full time lead founding dev at a cyber security saas startup, with 10 yoe and a bachelor's in CS. Building & debugging software products is what I've spent my time on for forever Yovel Cohen Yovel Cohen I got a lot of experience in building Long-horizon AI Agents in production, Backend apps that scale to millions of users and frontend knowledge as well. Matt Butler Matt Butler Software Engineer @ AWS MFox MFox Full-stack professional senior engineer (15+years). Extensive experience in software development, qa, and IP networking. Matthew Butler Matthew Butler Systems Development Engineer @ Amazon Web Services Antriksh Narang Antriksh Narang 5 years+ Experienced Dev (Specially in Web Development), can help in python, javascript, react, next.js and full stack web dev technologies. Jaime Orts-Caroff Jaime Orts-Caroff I'm a Senior Android developer, open to work in various fields Jen Jacobsen Jen Jacobsen I’m a Full-Stack Developer with over 10 years of experience building modern web and mobile applications. I enjoy working across the full product lifecycle — turning ideas into real, well-built products that are intuitive for users and scalable for businesses. I particularly enjoy building mobile apps, modern web platforms, and solving complex technical problems in a way that keeps systems clean, reliable, and easy to maintain.

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Frequently Asked Questions

How serious is this?

Very serious. This is a data privacy violation that could have legal consequences (GDPR, etc.). Fix it immediately and consider notifying affected users if sensitive data was exposed.

Can this be fixed without rebuilding the app?

Yes. Adding proper RLS policies (for Supabase) or API-level authorization checks can fix this without a rebuild. A developer can usually fix it within a day.

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