A coupon code is a short token entered during signup or checkout to apply a discount, unlock a promotion, or change pricing for a limited time. In normal commerce, the code is tied to specific terms such as eligibility, expiry date, and eligible products or plans.
In cyber security, coupon codes matter because they are a common target for abuse. Attackers may guess weak codes, reuse leaked codes, or lure users to fake promotion pages that steal account details. Defenders protect against this by validating codes on the server, enforcing rate limits, checking expiry and eligibility, and showing clear terms before payment. Careful verification is important whenever a code affects billing, because a hidden rule or fraudulent page can turn a discount into a scam or a pricing dispute.