A list of assets could be updated, so the actual one you can get from API.
Currently oracles nodes fetching price from Binance only. Oracle node application published in our Github repository and we are welcome for contributions: dfinance needs more exchanges and ticker pairs.
Every block dfinance platform collect posted prices from whitelisted oracles and then choose median to store final price for the last block.
This functional implemented by dnode in x/oracle module.