Your company, TechSolutions Inc., is developing a new e$-$commerce platform using a microservices architecture. The platform includes various services such as user authentication, product catalog, order processing, payment gateway, and customer reviews. Each service is developed and deployed independently.

During a security audit, it was discovered that the order processing service is vulnerable to a man$-$in$-$the$-$middle $($MITM$)$ attack. This vulnerability could potentially allow an attacker to intercept and manipulate order data, leading to unauthorized access to sensitive customer information and financial transactions.

As the lead security engineer, how would you address this vulnerability in the order processing service?

Explain your answer with a suitable labelled diagram.