Token approvals are permissions that you grant dApps by signing a message (sometimes unwittingly). Token approvals are not in themselves dangerous but they can be used by malicious actors to steal your NFTs or cryptocurrency. As such, oit's best to periodically check your token approvals. If you suspect you connected to a malicious website, check your token approvals immediately and revoke anything that looks suspicious!
Getting into the habit of checking your token approvals is a Web 3 security best practice.
There are various tools out there which allow you to revoke your token approvals. On Ethereum you can use Etherscan's token approval tool.
Connecting your wallet to the site above will allow you to see your token approvals. Navigate the tabs to see the token approvals for ERC-20, ERC-721, and ERC-1155 tokens you have in your wallet. Simply click "Revoke" to revoke the token approval. This will prompt a signature request on your wallet which you must complete.
On Solana, the most common tool to revoke token approvals which people use is Famous Fox Federation's Revoker tool. Simply connect your wallet and you will see your token approvals. You can then select the ones you want to revoke or click "Revoke all"