supabase

Supabase RLS playbook

Supabase exposes PostgreSQL directly to the browser through PostgREST (/rest/v1/), GoTrue auth (/auth/v1/), and Storage (/storage/v1/). The browser authenticates with a public anon JWT, and the only thing standing between an anonymous attacker and the database is Row-Level Security (RLS) policies. Misconfigured or missing RLS is the entire bug class:

• RLS disclosure — SELECT on a table returns rows it shouldn't (PII, tokens, other tenants).
• RLS write abuse — INSERT / UPDATE / DELETE succeeds anonymously, so you can forge records the application trusts (a "certificate" / verification / license / entitlement row, an admin flag, a balance, someone else's data).

Authorized targets only. Treat the database as production: read a single marker row to prove disclosure, write ONE clearly-labelled marker row to prove write, then clean up. Never dump whole tables of real PII, never mass-modify, never DELETE real rows. The PoC is "I read/wrote one row I shouldn't be able to", not "I exfiltrated the customer base".

Execution rule: substitute the real Supabase project ref, anon key, table, and marker IDs before running commands. Never write literal placeholders such as <ref>, <table>, <col>, or <returned-id> to files; if a value is unknown, discover it first or ask once.

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0. Find the project URL + anon key in the frontend JS

The project ref and anon key are meant to be public — they ship in the client bundle. You need both before you can talk to the API.

# Pull the main page + every script it references, then grep for the markers.
curl -ksS "https://TARGET/" -o /tmp/sb_index.html
grep -oE 'src="[^"]+\.js"' /tmp/sb_index.html | sed 's/src="//;s/"//' > /tmp/sb_js.txt
# Fetch each bundle (use the http/web_fetch tool or curl) into /tmp/sb_bundles/ ...

Grep the HTML and every JS bundle for:

# Project URL — gives you <ref>.supabase.co
grep -roE 'https://[a-z0-9]{20}\.supabase\.co' /tmp/sb_bundles/ | sort -u
grep -roiE 'supabase[._-]?url["'\'' :=]+[^"'\'' ,)]+'   /tmp/sb_bundles/

# Anon / service_role key — a JWT (eyJ...). Supabase keys decode to {"role":"anon"|"service_role"}
grep -roE 'eyJ[A-Za-z0-9_-]+\.eyJ[A-Za-z0-9_-]+\.[A-Za-z0-9_-]+' /tmp/sb_bundles/ | sort -u
grep -roiE 'supabase[._-]?(anon[._-]?)?key["'\'' :=]+[^"'\'' ,)]+' /tmp/sb_bundles/
grep -roiE 'createClient\([^)]*\)' /tmp/sb_bundles/