EXODUS apps are decentralized - they run on independent servers or directly on users' devices, not on a single corporate domain.
Your browser showed a warning because this service uses a self-signed certificate instead of one tied to a company domain. This is by design.
Your connection is still encrypted and secure. The warning simply means the certificate wasn't issued by a traditional authority - because decentralized apps don't need one.
This is how true decentralization works.