Oracle systems, which deliver off-chain data to smart contracts, are vital for the security of major on-chain lending platforms like Aave, Morpho, Euler, and Fluid. These systems ensure accurate price feeds, preventing unjust liquidations and protocol losses. The reliability of these oracles is critical, as any malfunction can lead to significant financial repercussions. Oracles operate in two main types: push-based, which regularly updates price data, and pull-based, which retrieves data on-demand. Each type has distinct cost, speed, and security characteristics. Leading oracles such as Chainlink, Chronicle, Pyth, and RedStone aggregate prices from multiple decentralized data providers to ensure secure delivery to blockchains. However, issues have occurred, including a Chainlink price misreport and a Pyth outage in 2025, resulting in unjust liquidations and losses.