Input Validation

If there is one overarching, primary security principle, it is this: Never Trust the User. In fact, we should write it like this:

NEVER TRUST THE USER

We understand that taking this viewpoint may seem overly negative or pessimistic. After all, our users are the reason that we create products and services in the first place. It almost seems disloyal not to trust them, as if we’re an overly suspicious shopkeeper who plasters “Camera Surveillance 24/7” and “Shoplifters Will Be Prosecuted to the Full Extent of the Law” signs all over his store and keeps an eagle eye on anyone who walks in his door. And what makes matters even worse is that we want—actually, we need—our users to trust us. We ask a lot from them. We ask them for their ...

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