diff --git a/server/api/controllers/__tests__/program-application.test.js b/server/api/controllers/__tests__/program-application.test.js
index f71ad31..ae723ac 100644
--- a/server/api/controllers/__tests__/program-application.test.js
+++ b/server/api/controllers/__tests__/program-application.test.js
@@ -221,7 +221,7 @@ describe('ProgramController.updateApplicationStatus', () => {
 
   it('updates on valid payload', async () => {
     programService.findBySlug.mockResolvedValue({ id: 'p1', name: 'Dogfooding' });
-    applicationService.getById.mockResolvedValue({ id: 'a1', status: 'submitted' });
+    applicationService.getById.mockResolvedValue({ id: 'a1', programId: 'p1', status: 'submitted' });
     applicationService.updateStatus.mockResolvedValue({ id: 'a1', status: 'accepted', projectId: 'proj-1' });
     notificationService.notifyProjectTeam.mockResolvedValue([]);
     const req = {
@@ -242,7 +242,7 @@ describe('ProgramController.updateApplicationStatus', () => {
 
   it('maps PostgREST no-rows error to 404', async () => {
     programService.findBySlug.mockResolvedValue({ id: 'p1', name: 'Dogfooding' });
-    applicationService.getById.mockResolvedValue({ id: 'missing', status: 'submitted' });
+    applicationService.getById.mockResolvedValue({ id: 'missing', programId: 'p1', status: 'submitted' });
     const err = Object.assign(new Error('no rows'), { code: 'PGRST116' });
     applicationService.updateStatus.mockRejectedValue(err);
     const req = {
@@ -257,7 +257,7 @@ describe('ProgramController.updateApplicationStatus', () => {
 
   it('calls notifyProjectTeam with application_accepted when submitted → accepted', async () => {
     programService.findBySlug.mockResolvedValue({ id: 'p1', name: 'Dogfooding 2026' });
-    applicationService.getById.mockResolvedValue({ id: 'app-1', status: 'submitted' });
+    applicationService.getById.mockResolvedValue({ id: 'app-1', programId: 'p1', status: 'submitted' });
     applicationService.updateStatus.mockResolvedValue({ id: 'app-1', status: 'accepted', projectId: 'proj-1' });
     notificationService.notifyProjectTeam.mockResolvedValue([]);
     const req = {
@@ -278,7 +278,7 @@ describe('ProgramController.updateApplicationStatus', () => {
 
   it('calls notifyProjectTeam with application_rejected when submitted → rejected', async () => {
     programService.findBySlug.mockResolvedValue({ id: 'p1', name: 'Dogfooding 2026' });
-    applicationService.getById.mockResolvedValue({ id: 'app-2', status: 'submitted' });
+    applicationService.getById.mockResolvedValue({ id: 'app-2', programId: 'p1', status: 'submitted' });
     applicationService.updateStatus.mockResolvedValue({ id: 'app-2', status: 'rejected', projectId: 'proj-2' });
     notificationService.notifyProjectTeam.mockResolvedValue([]);
     const req = {
@@ -299,7 +299,7 @@ describe('ProgramController.updateApplicationStatus', () => {
 
   it('does not call notifyProjectTeam when new status is submitted (no real transition)', async () => {
     programService.findBySlug.mockResolvedValue({ id: 'p1', name: 'Dogfooding 2026' });
-    applicationService.getById.mockResolvedValue({ id: 'app-3', status: 'submitted' });
+    applicationService.getById.mockResolvedValue({ id: 'app-3', programId: 'p1', status: 'submitted' });
     applicationService.updateStatus.mockResolvedValue({ id: 'app-3', status: 'submitted', projectId: 'proj-3' });
     const req = {
       params: { slug: 'dogfooding-2026', applicationId: 'app-3' },
@@ -314,7 +314,7 @@ describe('ProgramController.updateApplicationStatus', () => {
 
   it('still returns 200 even when notifyProjectTeam rejects', async () => {
     programService.findBySlug.mockResolvedValue({ id: 'p1', name: 'Dogfooding 2026' });
-    applicationService.getById.mockResolvedValue({ id: 'app-4', status: 'submitted' });
+    applicationService.getById.mockResolvedValue({ id: 'app-4', programId: 'p1', status: 'submitted' });
     applicationService.updateStatus.mockResolvedValue({ id: 'app-4', status: 'accepted', projectId: 'proj-4' });
     notificationService.notifyProjectTeam.mockRejectedValue(new Error('boom'));
     const req = {
@@ -327,20 +327,33 @@ describe('ProgramController.updateApplicationStatus', () => {
     expect(res.status).toHaveBeenCalledWith(200);
   });
 
-  it('still updates and returns 200 when the prior-status lookup (getById) fails', async () => {
+  it('404s (no write) when the application belongs to a DIFFERENT program (IDOR)', async () => {
     programService.findBySlug.mockResolvedValue({ id: 'p1', name: 'Dogfooding 2026' });
-    applicationService.getById.mockRejectedValue(new Error('supabase transport error'));
-    applicationService.updateStatus.mockResolvedValue({ id: 'app-5', status: 'accepted', projectId: 'proj-5' });
+    // Application exists but is scoped to another program.
+    applicationService.getById.mockResolvedValue({ id: 'other', programId: 'p2', status: 'submitted' });
     const req = {
-      params: { slug: 'dogfooding-2026', applicationId: 'app-5' },
+      params: { slug: 'dogfooding-2026', applicationId: 'other' },
       body: { status: 'accepted' },
       user: { address: 'admin' },
     };
     const res = mockRes();
     await programController.updateApplicationStatus(req, res);
-    // The status update still succeeds; getById failure only skips the notify gate.
-    expect(applicationService.updateStatus).toHaveBeenCalled();
-    expect(res.status).toHaveBeenCalledWith(200);
+    expect(res.status).toHaveBeenCalledWith(404);
+    expect(applicationService.updateStatus).not.toHaveBeenCalled();
     expect(notificationService.notifyProjectTeam).not.toHaveBeenCalled();
   });
+
+  it('404s (no write) when the application does not exist', async () => {
+    programService.findBySlug.mockResolvedValue({ id: 'p1', name: 'Dogfooding 2026' });
+    applicationService.getById.mockResolvedValue(null);
+    const req = {
+      params: { slug: 'dogfooding-2026', applicationId: 'ghost' },
+      body: { status: 'accepted' },
+      user: { address: 'admin' },
+    };
+    const res = mockRes();
+    await programController.updateApplicationStatus(req, res);
+    expect(res.status).toHaveBeenCalledWith(404);
+    expect(applicationService.updateStatus).not.toHaveBeenCalled();
+  });
 });
diff --git a/server/api/controllers/program.controller.js b/server/api/controllers/program.controller.js
index d0cecaa..7921e07 100644
--- a/server/api/controllers/program.controller.js
+++ b/server/api/controllers/program.controller.js
@@ -120,15 +120,14 @@ class ProgramController {
         return res.status(404).json({ status: 'error', message: 'Program not found' });
       }
 
-      // Prior-status lookup feeds only the notification gate below — a failure
-      // here must not break the status update or change the HTTP response.
-      let prevStatus;
-      try {
-        const existing = await programApplicationService.getById(applicationId);
-        prevStatus = existing?.status;
-      } catch (err) {
-        logger.error('Failed to read application prior status for notification gating:', err);
+      // Cross-check program scoping: an application from program B must not be
+      // updatable via program A's slug (IDOR). Authoritative — reject before any
+      // write. The fetched row also feeds the prior-status notification gate.
+      const existing = await programApplicationService.getById(applicationId);
+      if (!existing || existing.programId !== program.id) {
+        return res.status(404).json({ status: 'error', message: 'Application not found' });
       }
+      const prevStatus = existing.status;
 
       const reviewedBy = req.user?.address || req.auth?.address || 'unknown';
       const updated = await programApplicationService.updateStatus({
diff --git a/supabase/migrations/20260616000000_enable_rls_public_tables.sql b/supabase/migrations/20260616000000_enable_rls_public_tables.sql
new file mode 100644
index 0000000..793cd77
--- /dev/null
+++ b/supabase/migrations/20260616000000_enable_rls_public_tables.sql
@@ -0,0 +1,28 @@
+-- Enable Row Level Security on every public table (deny-by-default).
+--
+-- WHY: the Supabase Data API (PostgREST) exposes the `public` schema to the
+-- `anon` / `authenticated` roles via the public anon key, which ships in the
+-- client bundle. With RLS disabled, that key can read AND write every public
+-- table, bypassing the Express API and its SIWS/admin auth. Verified on prod:
+-- anon could SELECT and DELETE/UPDATE projects, program_admins, multisig_*.
+--
+-- WHY THIS IS SAFE HERE: the browser never queries these tables — the client
+-- uses Supabase only for auth (supabase.auth.*), and ALL data access goes
+-- through the Express server using the SERVICE_ROLE key, which has BYPASSRLS.
+-- So enabling RLS with NO policies denies anon/authenticated while the server
+-- is unaffected. If a table ever needs direct anon/authenticated access, add an
+-- explicit policy for it.
+--
+-- Idempotent: ENABLE on an already-RLS-enabled table is a no-op.
+
+DO $$
+DECLARE r RECORD;
+BEGIN
+  FOR r IN
+    SELECT tablename
+    FROM pg_tables
+    WHERE schemaname = 'public'
+  LOOP
+    EXECUTE format('ALTER TABLE public.%I ENABLE ROW LEVEL SECURITY;', r.tablename);
+  END LOOP;
+END $$;