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Application & OT Security · Foundational

Client-Side Validation

Input checks performed in the browser or mobile app before data is sent to the server.

Definition

Client-side validation improves user experience but provides no security because users can modify or bypass the client with a proxy or direct API calls. All security validation and authorization must be repeated on the server.

Example

An attacker edits a request in an intercepting proxy to send a negative quantity that the browser form would have blocked.

Exam tip

Never rely on client-side controls for security; this is a frequent exam trap.

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