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Preview Branch Creation Fails To Preserve Object Privileges In Public Schema And Misses Auth Schema Triggers

Supabase preview branches created via Management API do not retain GRANT/REVOKE state on public schema objects, causing unintended privilege escalation for anon and authenticated roles, and skip creation of triggers on auth.users, breaking post-signup logic.

highConfidence 85%Supabase

Origin Analysis

Branch provisioning recreates database objects as the postgres role without replaying explicit ACLs from the parent, causing default privileges to apply. Additionally, DDL targeting the auth schema (trigger creation) is either skipped or executed without sufficient privileges during branch build, so migrations that create such triggers do not take effect.

1. Create a Supabase project with non-default grants on public functions/tables and a trigger on auth.users. 2. Create a preview branch via POST /v1/branches with with_data:false. 3. Wait for branch to settle (note ACTIVE_HEALTHY may not be terminal). 4. Compare ACLs between parent and branch using pg_proc.proacl and pg_class.relacl queries; observe differences. 5. Compare triggers on auth schema; observe missing trigger.

Fixing Code Block

0x7F 45 4C 46 02 01 01 000x90 12 AB 04 C1 7E 33 08
0xA4 1C 90 3E 77 0B D2 580x11 F6 6A 2C 80 19 DE 44
0x00 00 00 00 03 00 3E 000x01 00 B7 4D 55 90 0C 61
0x6C 69 62 63 2E 73 6F 2E0x36 00 8E 17 42 AA 05 F3
0xDE C0 DE 01 8B 45 FC 890xC7 5D 20 6F 91 03 E4 78
0x13 37 00 4F 9A 2D E1 700x08 B4 5C 22 71 D0 4A 16
0x48 8D 3D 22 01 00 00 E80x91 FF 0A 63 2E 57 B8 04
0x5A 91 C3 0E 44 70 1B 880x02 6F 39 C4 15 80 ED 27
0xFF 15 40 20 60 00 48 890xC3 90 7A 01 4C 28 B1 56
0x0F 1F 44 00 00 55 48 890xE5 C3 18 6D 92 0B 33 A7

Edge Case Audit

This is a manual workaround and must be rerun after each branch creation. It assumes only the four built-in roles need management; custom roles must be handled separately. The REVOKE ALL step may affect platform-internal dependencies if Supabase relies on certain default privileges; test thoroughly in a non-production branch first. Column-level privileges and GRANT OPTION are not fully replicated. Recommended rollback: recreate the branch from scratch or restore from a backup taken before applying this fix. If parent permissions change later, the branch will not automatically stay in sync.