Product Interface Requirements

This question asks whether users interact with your solution through any kind of interface - a web application, mobile app, desktop software, API, or even command-line tools. Essentially, they want to know if there's any way for users to directly interact with your product, as opposed to you providing purely behind-the-scenes services. Most SaaS products have interfaces (that's how customers use them!), but some solutions work entirely in the background or are pure consulting services without any software component.

Having an interface means you're responsible for interface-level security - authentication, session management, input validation, and protecting against attacks like cross-site scripting or SQL injection. Each interface type brings unique security considerations and compliance requirements. Web interfaces need HTTPS and secure cookies, mobile apps require secure storage and transmission, and APIs need robust authentication and rate limiting. This impacts your development costs, security testing needs, and the depth of security reviews during customer procurement. However, direct interfaces also enable self-service adoption, reduce support burden, and allow for better user experience control.

Companies often forget that APIs count as interfaces - even if only your customer's developers use them. Another mistake is overlooking administrative or support interfaces that your own team uses to manage the service. Each interface is a potential attack surface that needs security controls. Some companies also fail to consider that different interface types may require different security assessments, leading to incomplete security documentation that delays deals.