Fix cross-site scripting in C# and ASP.NET Core
===============================================

Let Razor's @ encode the output: @Model.Name and @Model.Bio HTML-encode & < >
" ' and more, in text and in a quoted attribute. Never @Html.Raw on user data.
A link needs more than encoding: allow only http and https URLs, because
encoding leaves javascript:alert(1) working.

Page: https://softwaresecurity.com/fix/xss/csharp-aspnetcore/

What is in this archive
-----------------------
xss/csharp-aspnetcore/   the project: three implementations of the same code and one test suite
  src/Profiles/Views/Profile/Vulnerable.cshtml   (vulnerable)
  src/Profiles/Views/Profile/Fixed.cshtml   (fixed)
  src/Profiles/Views/Profile/Wrong.cshtml   (a plausible fix that still fails)
run-all.mjs   runs the tests in all three modes and checks the results (Node.js only)
LICENSE-CODE.txt

Run it
------
  Tested with .NET 10.0.12 (SDK 10.0.112). run-all.mjs needs Node.js 22 or
  later. Supported versions: https://softwaresecurity.com/fix/versions/

  From the xss/csharp-aspnetcore folder, install the dependencies once (this
  needs network access):

    dotnet restore tests/Profiles.Tests --locked-mode

  Then run the tests. IMPL chooses the implementation the tests load:

    # every test passes
    IMPL=fixed dotnet test --project tests/Profiles.Tests --no-restore --results-directory reports --report-xunit-junit --report-xunit-junit-filename junit.xml
    # an exploit test fails
    IMPL=vulnerable dotnet test --project tests/Profiles.Tests --no-restore --results-directory reports --report-xunit-junit --report-xunit-junit-filename junit.xml
    # a test fails
    IMPL=wrong dotnet test --project tests/Profiles.Tests --no-restore --results-directory reports --report-xunit-junit --report-xunit-junit-filename junit.xml

  The JUnit report is written to reports/junit.xml. To run all three modes and
  check the results in one step, run the harness from this top folder (it needs
  only Node.js; --install runs the install step first):

    node run-all.mjs --install xss/csharp-aspnetcore
    node run-all.mjs xss/csharp-aspnetcore

Verified
--------
  11 October 2026, with dotnetSdk 10.0.112, dotnetRuntime 10.0.12,
  aspNetCoreMvcTesting 10.0.12, xunitV3 4.0.1, angleSharp 1.8.2, semgrep
  1.180.0. Versions and results hold for that date: run the tests with your own
  versions before relying on the fix.

Licence
-------
  The code is MIT licensed (LICENSE-CODE.txt). The page text is CC BY 4.0.
