Notification Bugs
// 2 bugs
Bugs in email delivery, push notifications, in-app alerts, webhooks, and notification preferences.
// Why it matters
Notification bugs either flood users with duplicate messages or fail to notify them when something important happens. Duplicate emails after a retry, a notification sent after a user unsubscribes, or a broken email link all damage user trust and can create compliance issues.
// Common symptoms
- User receives the same email notification twice
- Notification is sent after the user has opted out or unsubscribed
- Email contains an expired or broken link
- Push notification is not delivered or is significantly delayed
- In-app notification count does not match the actual number of unread items
- Notification is sent for an action that was subsequently cancelled
// Bugs in this category
Showing 2 of 2 bugs
A user receives two identical email notifications triggered by a single event. This happens either because the notification job retries on a transient failure without checking whether the email was already delivered, or because two separate code paths both trigger an email for the same event — one synchronously and one via a background queue.
An order confirmation email for order 501 is delivered to user-b@example.com instead of the order owner user-a@example.com. The notification service resolves the recipient's email address from an in-memory cache that still holds user-b's address from a previous lookup. Because the cache is not invalidated when a user updates their email, stale address data is used for outgoing notifications.
// Explore other categories
Authentication Bugs
Bugs in login, logout, password reset, session management, tokens, and multi-factor flows.
Permission and Authorization Bugs
Bugs where users can access, edit, delete, or view resources they shouldn't be allowed to.
API Bugs
Bugs in HTTP status codes, request validation, response schemas, error messages, and API contracts.
UI and Frontend Bugs
Bugs affecting layout, forms, responsiveness, error messages, and how the interface behaves across browsers and screen sizes.
Data Bugs
Bugs involving incorrect, duplicated, stale, missing, or inconsistent data across the application.
Payment Bugs
Bugs in checkout flows, payment retries, webhooks, refunds, subscriptions, and invoices.
Time and Date Bugs
Bugs caused by timezone mismatches, daylight saving transitions, date range errors, and locale differences.
Search and Filter Bugs
Bugs in search results, filters, pagination, sorting, and result counts.
File Upload Bugs
Bugs in file type validation, size limits, upload progress, storage, and file preview.
// Practise finding these bugs
Hunt notification bugs hands-on in a live practice app, then check your findings against the seeded-bug answer guide.