Due to changes in Chromium’s security policy, communication with localhost is no longer trusted.
At present, the only secure way to enable communication between the web and a local environment is through Native Messaging Hosts.

Using Native Messaging Hosts also eliminates the need for a constantly running background process, which helps reduce potential issues and improves stability.
For example, Dropbox adopted this approach several years ago.

We strongly recommend that Box also migrate Box Tools to Native Messaging Hosts.