Architecture & practice·Risk, blast radius and change
the feature added one endpoint, and that endpoint took a file path from the client.
Attack surface
Everything an untrusted party can reach and influence — endpoints, parameters, file uploads, dependencies, admin tools, the CI system. It grows quietly with every convenience added, and shrinking it is usually cheaper than defending it. It belongs in ordinary design review, not only security review, because the least defensible surface is the one nobody realised they had added.