Many DeFi protocols and products that are capable of accepting your deposits are protected by an "admin key". This key is typically an Ethereum smart contract that is capable of upgrading the protocol or product in many ways.
Most admin keys are provably protected by features such as timelocks and multi-sigs. However, no DeFi project can prove the operational security of their admin key is strong.
This means that the only way that you can truly feel secure while using these DeFi products currently is to trust in the competency of the team and their ability to secure their admin key.
Please watch this video for more detail: