Blockchains are secure systems because they're isolated systems. But smart contracts aren't very exciting without data from the real world. Oracles are the bridges to supply data from the real world to the blockchain world.

However, a system is only as strong as its weakest link. You'd want the same security guarantees as what blockchain can provide. So the blockchain needs to "trust" oracles to deliver the correct data that's immune to manipulations.

With the rise of smart contracts and full automations, I think oracles will play a huge role in all of this.

The leading project that's working on this is Chainlink.