Скачать или смотреть A Single Line of Legacy Code Left Our App Wide Open

In this episode of Fix The Buggy Habits, I share a real-world story from my experience as a software developer at a mid-sized tech company in Leeds. What seemed like a harmless piece of legacy code turned into a critical security vulnerability — and it all came down to a single overlooked line.

During a new front-end rollout, I reused an old helper function without realizing it contained a leftover development shortcut: if (!isAuthenticated) return true;. This single condition effectively bypassed authentication across the app. Because tests didn’t catch the edge case and reviewers assumed the helper was safe, the bug slipped through and reached production.

For over a week, our admin dashboard was exposed to unauthenticated users. This experience taught me the risks of blindly trusting legacy code, why auth logic demands extra scrutiny, and how one misplaced line can compromise an entire security model. If you’re a developer, tester, or security engineer, this story is a reminder that vigilance matters — especially when dealing with authentication and legacy systems.

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