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Today I created a web application. I'm using this csp to avoid xss attacks. CSP: Content-Security-Policy", `child-src 'none'; connect-src 'none'; default-src 'none'; font-src 'none'; frame-src 'none'; img-src 'none'; manifest-src 'none'; media-src 'none'; object-src 'none'; prefetch-src 'none'; script-src 'report-sample'; style-src 'report-sample'; worker-src 'none'; Does anyone know if its still possible to xss? If so, how? My web app is an extremely simple pastebin website.

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    script-src 'report-sample' isn't that essentially not restricting script at all, but only report violations (there are non though since there are no restrictions). Also, why do you explicitly set all the policies explicitly to 'none' given that you already have a default-src 'none'? Commented Jun 13, 2021 at 18:13
  • I have no idea, the more the better i guess
    – user259894
    Commented Jun 13, 2021 at 18:22
  • Essentially, your CSP disallows everything.
    – user163495
    Commented Jun 14, 2021 at 11:54
  • A good resource is csp-evaluator.withgoogle.com
    – jub0bs
    Commented Jul 19, 2021 at 10:36
  • Still an experiment, but a successful one: trusted types.
    – jub0bs
    Commented Jul 19, 2021 at 10:43

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It's not clear what you mean by bypassing CSP. XSS (injecting user controlled HTML code) is possible in case of rendering unescaping user input, but it is impossible to exploit XSS, since you have completely prohibited styles and scripts.

But Clickjacking is possible since an absence of frame-ancestors directive.
Form redirection is also possible, since there is no form-action directive.

Pls note that script-src 'report-sample'; completely forbids any script on page, and style-src 'report-sample'; forbids any CSS style.
Thus, it will be a site with default styles built into the browser and no interactive interaction with visitors.

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