Bancor V3 does not use external oracles for price discovery.
Bancor V3 pools calculate the EMA (Exponential Moving Average).
The EMA is a type of weighted moving average (WMA) that gives more weighting or importance to recent price data. The EMA is used to see price trends over time.
This was recently updated from the use of SMA (Simple Moving Average) which included time as a factor in calculating the SMA rate. This new calculation (EMA), is more resilient to price manipulation even on smaller pools.