Prevent Injection via Input Validation | Dataford Interview Questions

Write a function to validate and sanitize user input to prevent common injection vulnerabilities.

Implement sanitize_input(value) for single-line display text. Return a normalized, sanitized string, or None when the input is invalid. Normalize Unicode with NFKC, trim and collapse whitespace, reject empty values, values longer than 200 characters, and all Unicode control characters, then HTML-escape characters that could create markup. This policy addresses output-context markup injection; parameterized queries and safe process APIs are still required for SQL or shell inputs.

Constraints

value may be any object, but only strings are valid
The normalized, whitespace-collapsed value must contain between 1 and 200 characters
All Unicode control and formatting characters are rejected
The function returns either a sanitized string or None

Function Signature

def sanitize_input(value):

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Problem

Write a function to validate and sanitize user input to prevent common injection vulnerabilities.

Constraints

value may be any object, but only strings are valid
The normalized, whitespace-collapsed value must contain between 1 and 200 characters
All Unicode control and formatting characters are rejected
The function returns either a sanitized string or None

Function Signature

def sanitize_input(value):

Your question is Prevent Injection via Input Validation. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.