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🚨 CRITICAL: RLS Policy Vulnerability Allows Cross-User Data Access #35
Description
🚨 Critical Security Vulnerability: RLS Policy Breach
Summary
The current Row Level Security (RLS) policies contain a critical vulnerability that allows any anonymous user to access ALL other anonymous users' spending data, completely breaking user data isolation.
Vulnerability Details
Root Cause
The RLS policies use a wildcard pattern user_id LIKE 'anon_%' that matches ALL anonymous users instead of isolating individual users:
CREATE POLICY "Users can view own spending entries" ON public.spending_entries
FOR SELECT USING (user_id = current_setting('request.jwt.claims', true)::json->>'sub' OR user_id LIKE 'anon_%');Impact Assessment
- Severity: 🔴 CRITICAL
- Data Exposure: Complete cross-user data access for anonymous users
- Affected Tables:
spending_entries,categories - User Impact: ALL anonymous users can see each other's spending data
Proof of Concept
- Anonymous User A gets ID:
anon_abc123 - Anonymous User B gets ID:
anon_xyz789 - Both users can access each other's data because both match
user_id LIKE 'anon_%'
Additional Security Issues Identified
1. Mixed Authentication Systems
- Uses both Supabase anonymous auth AND client-side generated IDs
- Creates confusion and potential bypass mechanisms
- Client-side user IDs can be manipulated via localStorage
2. No Rate Limiting
- No protection against data scraping or abuse
- Anonymous users can perform unlimited database queries
Required Fixes
Immediate (Critical)
- Fix RLS policies to use exact user matching only
- Remove wildcard
anon_%patterns from all policies - Implement proper user isolation
High Priority
- Standardize on Supabase anonymous auth only
- Remove client-side user ID generation
- Remove localStorage user_id manipulation
Medium Priority
- Add rate limiting and abuse prevention
- Implement audit logging
- Add security monitoring
Proposed Solution
1. Fix RLS Policies
-- Remove dangerous wildcard, use exact match only
CREATE POLICY "Users can view own spending entries" ON public.spending_entries
FOR SELECT USING (user_id = auth.jwt()->>'sub');2. Standardize Authentication
- Use only Supabase's built-in anonymous authentication
- Remove all client-side user ID generation
- Remove localStorage user_id storage
Files Affected
SUPABASE_SETUP.md- Contains vulnerable RLS policiessrc/composables/useAuth.ts- Mixed authentication logic- All database policies need immediate review
Priority
This is a production-critical security vulnerability that must be addressed immediately before any further development or deployment.
🤖 Generated with Claude Code
Activity
security: fix critical RLS vulnerability and standardize authentication
security: fix critical RLS vulnerability and standardize authenticati…
security: fix critical RLS vulnerability and standardize authenticati…
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