Most API breaches occur because systems trust valid requests too readily, rather than because attackers break in.
Common wrong belief: If authentication works, the API is secure. Uncomfortable truth: Attackers usually don’t bypass security; they use it correctly and abuse what you forgot to question.
Most developers imagine API breaches as dramatic events: broken encryption, stolen secrets, brute-force attacks. That image is comforting because it suggests security is about blocking outsiders.
In real systems, the majority of API incidents involve valid tokens, correct headers, and expected flows. The attacker isn’t fighting the system. They’re cooperating with it.
Why? Because APIs are built on trust layers:
- You trust the identity provider.
- You trust the token.
- You trust that authorised users will behave reasonably.
That last assumption is where things collapse.
An API doesn’t think in intent. It evaluates rules. If a request matches the rules, it passes. It doesn’t ask why the data is requested, how often, or whether the access pattern makes sense. Those are human assumptions, and systems don’t enforce what you don’t define.
This is why breaches often look boring in postmortems:
- User accessed data they were allowed to see.
- No rate limit was triggered.
- No authentication failure occurred.
Everything worked.
The mistake wasn’t missing HTTPS or OAuth. It was believed that authentication equals safety. It doesn’t. Authentication only answers who. It says nothing about should, scope, frequency, or impact.
Senior engineers learn this the hard way: security failures are often the result of design failures. They happen when systems are permissive by default and restrictive only in theory.
If your API trusts tokens more than it understands behaviour, it’s not secure, it’s polite.
And politeness is expensive at scale.
This is the difference between writing code and building systems.
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