Unlimited Approval is a feature that enables users to grant platforms and smart contracts the permission to spend tokens/ coins on your behalf without limit. Normally, when swapping on a specific AMM such as Uniswap, users need to approve the smart contract/ platform to transfer those tokens on their behalf.
When giving these platforms/ smart contracts unlimited approval, users will face 2 main risks: malicious projects and bug exploits. This risk gives hackers the right to use the approved tokens for many lucrative purposes.