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[Blazor] Security - interactive-server-side-rendering - script tags #34202

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[Blazor] Security - interactive-server-side-rendering - script tags #34202

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1 change: 0 additions & 1 deletion aspnetcore/blazor/security/interactive-server-side-rendering.md
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Expand Up @@ -392,7 +392,6 @@ In addition to the safeguards that the framework implements, the app must be cod
For a XSS vulnerability to exist, the app must incorporate user input in the rendered page. Blazor executes a compile-time step where the markup in a `.razor` file is transformed into procedural C# logic. At runtime, the C# logic builds a *render tree* describing the elements, text, and child components. This is applied to the browser's DOM via a sequence of JavaScript instructions (or is serialized to HTML in the case of prerendering):

* User input rendered via normal Razor syntax (for example, `@someStringValue`) doesn't expose a XSS vulnerability because the Razor syntax is added to the DOM via commands that can only write text. Even if the value includes HTML markup, the value is displayed as static text. When prerendering, the output is HTML-encoded, which also displays the content as static text.
* Script tags aren't allowed and shouldn't be included in the app's component render tree. If a script tag is included in a component's markup, a compile-time error is generated.
* Component authors can author components in C# without using Razor. The component author is responsible for using the correct APIs when emitting output. For example, use `builder.AddContent(0, someUserSuppliedString)` and *not* `builder.AddMarkupContent(0, someUserSuppliedString)`, as the latter could create a XSS vulnerability.

Consider further mitigating XSS vulnerabilities. For example, implement a restrictive [Content Security Policy (CSP)](https://developer.mozilla.org/docs/Web/HTTP/CSP). For more information, see <xref:blazor/security/content-security-policy>.
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