micromark-extension-gfm-tagfilter

micromark extension to support GFM tag filter.

Contents

• What is this?
• When to use this
• Install
• Use
• API
  • gfmTagfilterHtml()
• Authoring
• HTML
• CSS
• Syntax
• Types
• Compatibility
• Security
• Related
• Contribute
• License

What is this?

This package contains an extension that adds support for the tagfilter enabled by GFM to micromark. The tagfilter is kinda weird and kinda useless. This package exists for completeness. The tag filter is a naïve attempt at XSS protection. You should use a proper HTML sanitizing algorithm.

When to use this

This project is useful when you want to match how GitHub works. You can use this extension when you are working with micromark already. When you do, you can instead use micromark-extension-gfm, which includes this extension, to support all GFM features.

When you want to deal with syntax trees, you should instead use hast-util-sanitize.

When you use remark and rehype, you should use rehype-sanitize.

Install

This package is ESM only. In Node.js (version 16+), install with npm:

1npm install micromark-extension-gfm-tagfilter

In Deno with esm.sh:

1import {gfmTagfilterHtml} from 'https://esm.sh/micromark-extension-gfm-tagfilter@2'

In browsers with esm.sh:

1<script type="module">
2  import {gfmTagfilterHtml} from 'https://esm.sh/micromark-extension-gfm-tagfilter@2?bundle'
3</script>

Use

1import {micromark} from 'micromark'
2import {gfmTagfilterHtml} from 'micromark-extension-gfm-tagfilter'
3
4const output = micromark('XSS! <script>alert(1)</script>', {
5  allowDangerousHtml: true,
6  htmlExtensions: [gfmTagfilterHtml()]
7})
8
9console.log(output)

Yields:

1<p>XSS! &lt;script>alert(1)&lt;/script></p>

API

This package exports the identifier gfmTagfilterHtml. There is no default export.

gfmTagfilterHtml()

Create an HTML extension for micromark to support GitHubs weird and useless tagfilter when serializing to HTML.

Returns

Extension for micromark that can be passed in htmlExtensions to support GitHubs weird and useless tagfilter when serializing to HTML (HtmlExtension).

Authoring

This package relates to malicious authors, not decent authors.

HTML

GFM tagfilter removes certain dangerous HTML tags: iframe, noembed, noframes, plaintext, script, style, title, textarea, and xmp.

CSS

This package does not relate to CSS.

Syntax

This package does not change how markdown is parsed.

Types

This package is fully typed with TypeScript. It exports no additional types.

Compatibility

Projects maintained by the unified collective are compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, micromark-extension-gfm-tagfilter@^2, compatible with Node.js 16.

This package works with micromark version 3 and later.

Security

While micromark is safe by default, this extension only does something when allowDangerousHtml: true is passed, which is an unsafe option. This package is not safe.

Related

• micromark-extension-gfm — support all of GFM
• hast-util-sanitize — hast utility to make trees safe
• rehype-sanitize — rehype plugin to sanitize HTML

Contribute

See contributing.md in micromark/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.

License

MIT © Titus Wormer