Common Design-Level Security Failures

One prevalent design flaw involves insufficient rate limiting and resource control. Applications that allow unlimited login attempts, API calls, or resource consumption invite abuse. For instance, a password reset feature that doesn't limit attempts enables attackers to flood users with reset emails or brute-force reset tokens. It's like having a door that allows infinite key attempts—eventually, someone will find the right combination.

Another critical design failure occurs when applications trust client-side controls for security decisions. Designing an e-commerce system where prices are validated only in the browser, or a game where scores are calculated client-side, invites manipulation. These aren't coding errors—they're fundamental misunderstandings of the trust model in web applications. The design itself assumes users won't tamper with client-side code, ignoring the reality that attackers have complete control over their browsers and can modify any client-side logic.