Which vulnerability occurs when input from a client is not validated before being processed by web applications and backend servers?

Which vulnerability occurs when input from a client is not validated before being processed by web applications and backend servers?

• A. Unvalidated Inputs
• B. Parameter/Form Tampering
• C. Improper Error Handling
• D. Web Service Attack

Answer: (A)

Unvalidated input means the application accepts data from a user without checking that it’s safe, well-formed, or within expected boundaries before it’s processed by the web app or backend services. When input isn’t validated, crafted data can influence queries, commands, or file paths, leading to injections, logic errors, or data exposure. Validating and sanitizing input—using strict allow-lists, enforcing types and length checks, and parameterizing downstream calls—helps prevent these issues. This description matches unvalidated inputs precisely: client data is accepted and processed without proper validation. The other issues describe different problems—tampering is about altering request data to gain advantage, improper error handling concerns leaking or mismanaging errors, and web service attacks cover broader service-targeted exploits.

Unvalidated input means the application accepts data from a user without checking that it’s safe, well-formed, or within expected boundaries before it’s processed by the web app or backend services. When input isn’t validated, crafted data can influence queries, commands, or file paths, leading to injections, logic errors, or data exposure. Validating and sanitizing input—using strict allow-lists, enforcing types and length checks, and parameterizing downstream calls—helps prevent these issues. This description matches unvalidated inputs precisely: client data is accepted and processed without proper validation. The other issues describe different problems—tampering is about altering request data to gain advantage, improper error handling concerns leaking or mismanaging errors, and web service attacks cover broader service-targeted exploits.