Their is no guarantee that the Dapp and the associated smart contracts are free from any security vulnerabilities. The entire code base is open source and any scrutiny is appreciated.
A. Currently the Dapp is on Cardano's 'preprod' network. Kindly make sure that when interacting with Dapp functionality, you are on that network. Use 'mainnet' network to test NuFi On/Off Ramp and Dex integration.
B. Use HTTPS and for best experience, try to have your system clock close to actual.