Sanitizing the Rich Text Editor

This section describes how to sanitize the Rich Text Editor serverside

The Rich Text Editor is sanitized on the frontend by default, however, you may want to do this serverside as well. The libraries that are out there tend to have strict dependencies. That is why we will leave it up to you how you want to sanitize the HTML.

Implementing your own IHtmlSanitizer

We have added an abstraction called IHtmlSanitizer, which by default does nothing. You can override it with your own implementation to handle sanitization as you see fit. This interface has a single method: string Sanitize(string html). The output of this method is what will be stored in the database when you save a Rich Text Editor.

To add your own sanitizer you must first create a class the implements the interface:

using Umbraco.Cms.Core.Security;

namespace MySite.HtmlSanitization;

public class MyHtmlSanitizer : IHtmlSanitizer
{
    public string Sanitize(string html)
    {
        // Sanitize the html parameter here
        return "<h1>Sanitized HTML</h1>";
    }
}

The Sanitize method in this implementation is where you can use a library. You could also use your own sanitizer implementation, to sanitize the Rich Text Editor input.

Now that you've added your own custom IHtmlSanitizer you must register it in the container to replace the existing NoOp sanitizer.

You can register it directly in the Program.cs or use a composer.

Learn more about registering dependencies and when to use which method in the Dependency Injection article.

The extension method could look like the following:

using Umbraco.Cms.Core.DependencyInjection;
using Umbraco.Cms.Core.Security;
using Umbraco.Extensions;

namespace MySite.HtmlSanitization;

public static class BuilderExtensions
{
    public static IUmbracoBuilder AddHtmlSanitizer(this IUmbracoBuilder builder)
    {
        builder.Services.AddUnique<IHtmlSanitizer, MyHtmlSanitizer>();
        return builder;
    }
}

The extension can then be invoked in the CreateUmbracoBuilder() builder chain in the Program.cs file:

builder.CreateUmbracoBuilder()
    .AddBackOffice()
    .AddWebsite()
    .AddDeliveryApi()
    .AddComposers()
    .AddHtmlSanitizer() // Call you extension method here.
    .Build();

Or you can use a Composer:

using Umbraco.Cms.Core.Composing;
using Umbraco.Cms.Core.DependencyInjection;
using Umbraco.Cms.Core.Security;
using Umbraco.Extensions;

namespace MySite.HtmlSanitization;

public class SanitizerComposer : IComposer
{
    public void Compose(IUmbracoBuilder builder)
    {
        builder.Services.AddUnique<IHtmlSanitizer, MyHtmlSanitizer>();
    }
}

With your custom sanitizer in place the Rich Text Editor will always contain the "Sanitized HTML" heading. This shows that everything is working as expected, and that whatever your sanitizer returns is what will be saved.