Welcome to your interview.
The question is on your right: Injection-Safe Input Validation. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.
Implement a secure input validation helper function in Ruby or Go that mitigates injection vulnerabilities in a multi-tenant application.