In Express.js application the code is sensitive if the https://www.npmjs.com/package/helmet-csp[helmet-csp] or https://www.npmjs.com/package/helmet[helmet] middleware is used without the ``++frameAncestors++`` directive (or if ``++frameAncestors++`` is set to ``++'none'++``):
In Express.js application a standard way to implement CSP frame-ancestors directive is the https://www.npmjs.com/package/helmet-csp[helmet-csp] or https://www.npmjs.com/package/helmet[helmet] middleware: