🔒 [security] Replace predictable invoice numbers with secure random identifiers by syed-reza98 · Pull Request #398 · CodeStorm-Hub/stormcomui

syed-reza98 · 2026-03-30T13:48:51Z

🎯 What: The vulnerability fixed

Predictable invoice numbers and webhook challenges caused by the use of Math.random().

⚠️ Risk: The potential impact if left unfixed

Attackers could potentially predict future invoice numbers or spoof webhook verification challenges, leading to information leakage or unauthorized integration setups.

🛡️ Solution: How the fix addresses the vulnerability

Replaced Math.random() with cryptographically secure random strings generated by the Node.js crypto module. This ensures that the random components of these identifiers are non-deterministic and highly resistant to prediction attacks. I used base64url encoding for the invoice part to maintain a high character entropy while keeping the identifier compact.

PR created automatically by Jules for task 12485382378685279424 started by @syed-reza98

This change addresses a security vulnerability where invoice numbers and webhook verification challenges were generated using Math.random(), which is not cryptographically secure and could lead to predictable identifiers. Specifically: - Updated `src/lib/subscription/billing-service.ts` to use `crypto.randomBytes(4).toString('base64url')` for invoice numbers. - Updated `src/lib/integrations/facebook/webhook-manager.ts` to use `crypto.randomBytes(8).toString('hex')` for verification challenges. - Added a new unit test `src/test/services/billing-service.test.ts` to verify invoice number format and uniqueness. - Exported `createInvoiceForPayment` to support testing. - Restored accidental deletion of package-lock.json. Co-authored-by: syed-reza98 <71028588+syed-reza98@users.noreply.github.com>

google-labs-jules · 2026-03-30T13:48:53Z

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vercel · 2026-03-30T13:48:58Z

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Project	Deployment	Actions	Updated (UTC)
stormcomui	Ready	Preview, Comment	Mar 31, 2026 2:30pm

…85279424

Copilot

Pull request overview

This PR addresses predictability concerns in billing invoice numbers and Facebook webhook verification challenges by replacing Math.random() with Node.js crypto-based randomness, and adds a unit test around the invoice number format/uniqueness.

Changes:

Replaced Math.random() invoice suffix generation with crypto.randomBytes(...).toString('base64url') in the subscription billing service.
Replaced Math.random() challenge generation with crypto.randomBytes(...).toString('hex') in the Facebook webhook endpoint verification flow.
Added a Vitest unit test validating invoice number format and that successive calls produce different invoice numbers.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/lib/subscription/billing-service.ts	Switches invoice number generation to `crypto` and exports `createInvoiceForPayment` (used by the new unit test).
src/lib/integrations/facebook/webhook-manager.ts	Switches webhook verification `hub.challenge` generation to cryptographically-secure randomness.
src/test/services/billing-service.test.ts	Adds unit coverage for invoice number format and uniqueness using mocked Prisma.

Copilot · 2026-03-30T14:18:59Z

src/lib/subscription/billing-service.ts

+export async function createInvoiceForPayment(
  subscriptionId: string,


Exporting createInvoiceForPayment appears to be solely for unit testing (no other production references found). This increases the module’s public surface area; consider keeping the DB-writing function private and instead exporting/testing a small pure helper that generates the invoice number (or test via the existing public entrypoint that calls it).

Copilot · 2026-03-30T14:19:00Z

src/test/services/billing-service.test.ts

+      // RANDOM (5 chars ALPHANUMERIC-ish)
+      expect(invoiceNumber).toMatch(/^INV-\d+-[0-9A-Z_-]{5}$/);


This format assertion is tightly coupled to the current implementation (exactly 5 chars and forced uppercase). If the generator is strengthened (longer token, preserving base64url case), this test will fail even though behavior is still correct. Consider loosening the pattern (e.g., length >= N and base64url charset) and/or stubbing Date.now/randomBytes for a deterministic unit test.

Suggested change

// RANDOM (5 chars ALPHANUMERIC-ish)

expect(invoiceNumber).toMatch(/^INV-\d+-[0-9A-Z_-]{5}$/);

// RANDOM (>= 5 chars, base64url-safe charset)

expect(invoiceNumber).toMatch(/^INV-\d+-[A-Za-z0-9_-]{5,}$/);

Copilot · 2026-03-30T14:19:00Z

src/test/services/billing-service.test.ts

+      await createInvoiceForPayment(subscriptionId, amount, periodStart, periodEnd);
+      await createInvoiceForPayment(subscriptionId, amount, periodStart, periodEnd);
+
+      expect(prisma.invoice.create).toHaveBeenCalledTimes(2);
+      const firstCall = vi.mocked(prisma.invoice.create).mock.calls[0][0];
+      const secondCall = vi.mocked(prisma.invoice.create).mock.calls[1][0];
+
+      expect(firstCall.data.invoiceNumber).not.toBe(secondCall.data.invoiceNumber);


This test can be flaky because it relies on real randomness for uniqueness. Even if collisions are unlikely, it’s better to stub the random generator (and optionally Date.now) to return two different known values and assert the invoice numbers differ for the expected reason.

Suggested change

await createInvoiceForPayment(subscriptionId, amount, periodStart, periodEnd);

await createInvoiceForPayment(subscriptionId, amount, periodStart, periodEnd);

expect(prisma.invoice.create).toHaveBeenCalledTimes(2);

const firstCall = vi.mocked(prisma.invoice.create).mock.calls[0][0];

const secondCall = vi.mocked(prisma.invoice.create).mock.calls[1][0];

expect(firstCall.data.invoiceNumber).not.toBe(secondCall.data.invoiceNumber);

const dateNowSpy = vi.spyOn(Date, 'now').mockReturnValue(1_700_000_000_000);

const randomSpy = vi

.spyOn(Math, 'random')

.mockReturnValueOnce(0.1)

.mockReturnValueOnce(0.9);

try {

await createInvoiceForPayment(subscriptionId, amount, periodStart, periodEnd);

await createInvoiceForPayment(subscriptionId, amount, periodStart, periodEnd);

} finally {

dateNowSpy.mockRestore();

randomSpy.mockRestore();

}

expect(prisma.invoice.create).toHaveBeenCalledTimes(2);

const firstCall = vi.mocked(prisma.invoice.create).mock.calls[0][0];

const secondCall = vi.mocked(prisma.invoice.create).mock.calls[1][0];

const firstInvoiceNumber = firstCall.data.invoiceNumber as string;

const secondInvoiceNumber = secondCall.data.invoiceNumber as string;

const firstMatch = firstInvoiceNumber.match(/^(.+)-([0-9A-Z_-]{5})$/);

const secondMatch = secondInvoiceNumber.match(/^(.+)-([0-9A-Z_-]{5})$/);

expect(firstMatch).not.toBeNull();

expect(secondMatch).not.toBeNull();

if (!firstMatch || !secondMatch) return;

const firstPrefix = firstMatch[1];

const firstRandomPart = firstMatch[2];

const secondPrefix = secondMatch[1];

const secondRandomPart = secondMatch[2];

// With Date.now stubbed, the prefix (INV + timestamp) should be identical,

// and only the random suffix should differ between calls.

expect(firstPrefix).toBe(secondPrefix);

expect(firstRandomPart).not.toBe(secondRandomPart);

Copilot · 2026-03-30T14:19:01Z

src/lib/subscription/billing-service.ts

  periodEnd: Date
 ): Promise<void> {
-  const invoiceNumber = `INV-${Date.now()}-${Math.random().toString(36).slice(2, 7).toUpperCase()}`;
+  const randomPart = crypto.randomBytes(4).toString('base64url').toUpperCase().slice(0, 5);


The generated invoiceNumber still has very low entropy: 4 random bytes are encoded and then truncated to 5 chars (and uppercased), which is only ~26 bits of search space. If invoice numbers are meant to be unguessable, consider using a longer random segment (e.g., >=12 bytes) and avoid uppercasing/truncation that reduces the alphabet and discards entropy.

Suggested change

const randomPart = crypto.randomBytes(4).toString('base64url').toUpperCase().slice(0, 5);

const randomPart = crypto.randomBytes(12).toString('base64url');

…85279424

github-project-automation bot added this to StormCom Mar 30, 2026

github-project-automation bot moved this to Backlog in StormCom Mar 30, 2026

Merge branch 'main' into fix-predictable-invoice-numbers-124853823786…

46365d1

…85279424

syed-reza98 marked this pull request as ready for review March 30, 2026 14:13

Copilot AI review requested due to automatic review settings March 30, 2026 14:13

Copilot started reviewing on behalf of syed-reza98 March 30, 2026 14:14 View session

Copilot AI reviewed Mar 30, 2026

View reviewed changes

Merge branch 'main' into fix-predictable-invoice-numbers-124853823786…

c361dbc

…85279424

vercel bot had a problem deploying to Preview March 31, 2026 05:01 Failure

Merge branch 'main' into fix-predictable-invoice-numbers-124853823786…

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…85279424

vercel bot deployed to Preview March 31, 2026 14:30 View deployment

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🔒 [security] Replace predictable invoice numbers with secure random identifiers#398

🔒 [security] Replace predictable invoice numbers with secure random identifiers#398
syed-reza98 wants to merge 4 commits intomainfrom
fix-predictable-invoice-numbers-12485382378685279424

syed-reza98 commented Mar 30, 2026

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		export async function createInvoiceForPayment(
		subscriptionId: string,

		// RANDOM (5 chars ALPHANUMERIC-ish)
		expect(invoiceNumber).toMatch(/^INV-\d+-[0-9A-Z_-]{5}$/);

-      await createInvoiceForPayment(subscriptionId, amount, periodStart, periodEnd);
-      await createInvoiceForPayment(subscriptionId, amount, periodStart, periodEnd);
-      expect(prisma.invoice.create).toHaveBeenCalledTimes(2);
-      const firstCall = vi.mocked(prisma.invoice.create).mock.calls[0][0];
-      const secondCall = vi.mocked(prisma.invoice.create).mock.calls[1][0];
-      expect(firstCall.data.invoiceNumber).not.toBe(secondCall.data.invoiceNumber);
+      const dateNowSpy = vi.spyOn(Date, 'now').mockReturnValue(1_700_000_000_000);
+      const randomSpy = vi
+        .spyOn(Math, 'random')
+        .mockReturnValueOnce(0.1)
+        .mockReturnValueOnce(0.9);
+      try {
+        await createInvoiceForPayment(subscriptionId, amount, periodStart, periodEnd);
+        await createInvoiceForPayment(subscriptionId, amount, periodStart, periodEnd);
+      } finally {
+        dateNowSpy.mockRestore();
+        randomSpy.mockRestore();
+      }
+      expect(prisma.invoice.create).toHaveBeenCalledTimes(2);
+      const firstCall = vi.mocked(prisma.invoice.create).mock.calls[0][0];
+      const secondCall = vi.mocked(prisma.invoice.create).mock.calls[1][0];
+      const firstInvoiceNumber = firstCall.data.invoiceNumber as string;
+      const secondInvoiceNumber = secondCall.data.invoiceNumber as string;
+      const firstMatch = firstInvoiceNumber.match(/^(.+)-([0-9A-Z_-]{5})$/);
+      const secondMatch = secondInvoiceNumber.match(/^(.+)-([0-9A-Z_-]{5})$/);
+      expect(firstMatch).not.toBeNull();
+      expect(secondMatch).not.toBeNull();
+      if (!firstMatch || !secondMatch) return;
+      const firstPrefix = firstMatch[1];
+      const firstRandomPart = firstMatch[2];
+      const secondPrefix = secondMatch[1];
+      const secondRandomPart = secondMatch[2];
+      // With Date.now stubbed, the prefix (INV + timestamp) should be identical,
+      // and only the random suffix should differ between calls.
+      expect(firstPrefix).toBe(secondPrefix);
+      expect(firstRandomPart).not.toBe(secondRandomPart);

	const randomPart = crypto.randomBytes(4).toString('base64url').toUpperCase().slice(0, 5);
	const randomPart = crypto.randomBytes(12).toString('base64url');

Conversation

syed-reza98 commented Mar 30, 2026

🎯 What: The vulnerability fixed

⚠️ Risk: The potential impact if left unfixed

🛡️ Solution: How the fix addresses the vulnerability

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