Is a custom-built client dashboard/web app more vulnerable to hacking than keeping data and workflows inside a tool like Claude Code?

One member asked whether a custom dashboard pulling live client financial data is more hackable than keeping things inside Claude Code. The builder's answer: they used Claude itself to help address this and secured the site behind Cloudflare, described as one of the biggest security companies/products in the world. Access to the particular dashboard is restricted to five or six named people, and it requires sign-in through Gmail to authenticate. The underlying hosting is a Digital Ocean server, though the builder noted they are 'still not 100% sure' how all the server infrastructure works -- Claude directed the setup.