MEDIUM: No input validation on subscription amount — negative and NaN values accepted #9

New issue

Closed

opened 2026-05-09 00:02:36 +00:00 by Mark · 0 comments

Mark commented

2026-05-09 00:02:36 +00:00

Owner

Severity: Medium

Location

backend/src/controllers/SubscriptionController.ts lines 69–83

Description

The create method only checks if amount === undefined, allowing negative numbers, NaN, Infinity, and extremely large values:

if (!name || !billingDate || amount === undefined) {
  res.status(400).json({ error: 'Name, billing date, and amount are required' });
  return;
}
// ...
amount: Number(amount),

Number(amount) will silently convert strings like '' to 0, and Number(undefined) to NaN. There is no check that amount is a positive finite number.

Impact

Users could accidentally create subscriptions with negative or NaN amounts, crashing the dashboard display
A subscription with amount 0 or negative would skew financial calculations

Suggested Fix

Add proper validation:

const numAmount = Number(amount);
if (isNaN(numAmount) || numAmount < 0 || !isFinite(numAmount)) {
  res.status(400).json({ error: 'Amount must be a valid positive number' });
  return;
}

## Severity: Medium ## Location `backend/src/controllers/SubscriptionController.ts` lines 69–83 ## Description The `create` method only checks if `amount === undefined`, allowing negative numbers, NaN, Infinity, and extremely large values: ```typescript if (!name || !billingDate || amount === undefined) { res.status(400).json({ error: 'Name, billing date, and amount are required' }); return; } // ... amount: Number(amount), ``` `Number(amount)` will silently convert strings like `''` to 0, and `Number(undefined)` to NaN. There is no check that `amount` is a positive finite number. ## Impact - Users could accidentally create subscriptions with negative or NaN amounts, crashing the dashboard display - A subscription with amount 0 or negative would skew financial calculations ## Suggested Fix Add proper validation: ```typescript const numAmount = Number(amount); if (isNaN(numAmount) || numAmount < 0 || !isFinite(numAmount)) { res.status(400).json({ error: 'Amount must be a valid positive number' }); return; } ```