Blockchain Oracle

A blockchain oracle is a service that delivers outside information — prices, interest rates, sports results, weather, proof that a payment arrived — to a smart contract, because a blockchain cannot read the internet on its own. Contracts are deterministic and isolated by design, so any real-world data must first be published on-chain by an oracle before code can act on it. That makes the oracle a critical dependency: if a feed is wrong, stale or manipulated, lending protocols can liquidate healthy positions and derivatives can settle at the wrong price. Attackers have exploited thin markets to move a reported price for a few blocks. Serious protocols therefore use multiple independent sources, medians and sanity limits instead of trusting one feed.