HtmlSanitizer is a class for cleaning HTML fragments from constructs that can lead to XSS attacks. It uses the excellent C# jQuery port CsQuery to parse, manipulate, and render HTML and CSS.

In order to facilitate different use cases, HtmlSanitizer can be customized at several levels:

Configure allowed HTML tags through the property AllowedTags. All other tags will be stripped.
Configure allowed HTML attributes through the property AllowedAttributes. All other attributes will be stripped.
Configure allowed CSS property names through the property AllowedCssProperties. All other styles will be stripped.
Configure allowed URI schemes through the property AllowedCssProperties. All other URIs will be stripped.
Configure HTML attributes that contain URIs (such as "src", "href" etc.) through the property UriAttributes.
Provide a base URI that will be used to resolve relative URIs against.

Usage

Install the CsQuery NuGet package
Copy HtmlSanitizer.cs into your project

var sanitizer = new HtmlSanitizer();
var html = @"<script>alert('xss')</script><div onload=""alert('xss')"""
	+ @"style=""background-color: test"">Test<img src=""test.gif"""
	+ @"style=""background-image: url(javascript:alert('xss')); margin: 10px""></div>";
var sanitized = sanitizer.Sanitize(html, "http://www.example.com");
Assert.That(sanitized, Is.EqualTo(@"<div style=""background-color: test"">"
	+ @"Test<img style=""margin: 10px"" src=""http://www.example.com/test.gif""></div>");

License

MIT X11