How do I secure Stripe in an AI-built app?
Create checkout sessions on the server with prices from your own records, keep the secret key server-side, grant access only when a signature-verified webhook confirms payment, and make access follow subscription status on every request. The common AI-generated mistakes are trusting a price sent by the browser, granting access on the success page, and not verifying webhook signatures.
Mistakes and fixes
| Mistake | Fix |
|---|---|
| Price or plan taken from the request | Look up the price ID on the server |
| Access granted on reaching the success URL | Grant from the verified webhook |
| Webhook signature not verified | Verify with the endpoint secret |
| Secret key in front-end code | Server-only, rotate if exposed |
| Paid flag stored where users can edit | Protect plan fields with server rules |
| Cancellation does not remove access | Handle subscription update and delete events |
Canadian specifics
Charge GST or HST by province where you are registered; Stripe Tax can calculate it. Receipts must show it.
Testing your payment flow
Use Stripe's test mode and try what an attacker would. Change the price or plan ID in the request that creates the checkout session. Visit the success URL directly without paying. Replay a webhook request with a modified body. Cancel a subscription in the Stripe dashboard and check access ends. Use a test card that triggers a failed payment and see what state the account is left in. Downgrade and check paid features lock.
Each of these should fail safely. If visiting the success page grants access, or the price can be changed in the request, fix it before launch: those are the two payment findings that cost real money. Keep the webhook endpoint secret, rotate it if it leaks, and log every event you process so disputes can be traced.
Getting it checked
TrazTech offers vibe-coding QA and security review, listed from $2,000 CAD. Get at least one other quote on the same scope; the questions to ask a testing firm help compare them.
Related questions
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Get matchedCommon questions
Does Stripe handle security for me?
It secures card data. Whether your app grants access correctly is your code.
Is PCI DSS my problem?
With hosted Stripe Checkout or Elements, card data does not touch your servers, which keeps your PCI scope minimal.