The developers (and the team behind ZBeacon), any eavesdroppers, the government, cannot see your data due to the security strength of SHA3-512. The extension collects:

-Math.random() values
-Connection statistics, such as 4g or 3g, fiber optic or not, etc. (Connection API)
-Received HTTP Headers
-Sent HTTP Headers
-Entire visited website hash
-Operating System's CSPRNG. (Default cryptographically secure random number generator)
-Date, and time that the page has been opened for down to the microsecond.
-Timestamps from when the client did certain actions
-All JavaScript events

Do not be scared, NO ONE CAN READ THIS INFORMATION. We hash the data securely, we discard some bits from the hash in the server to serve the randomness to developers. In fact, the client hashes the data so that information is 100% secure and you don't need to trust the server either.
The hash basically gives us randomness and discards any information from the data. This extension is completely open source and you can review the code to make sure it's all lined up with this policy.
The servers we have do not have to be trusted. Even if they were compromised, the client hashes the data securely, so the server can't reverse it.