#Disallowed Raw HTML Extension

The DisallowedRawHtmlExtension automatically escapes certain HTML tags when rendering raw HTML, such as:

• <title>
• <textarea>
• <style>
• <xmp>
• <iframe>
• <noembed>
• <noframes>
• <script>
• <plaintext>

Filtering is done by replacing the leading < with the entity <.

This is required by the GFM spec because these particular tags could cause undesirable side-effects if a malicious user tries to introduce them.

All other HTML tags are left untouched by this extension.

#Installation

This extension is bundled with league/commonmark. This library can be installed via Composer:

composer require league/commonmark

See the installation section for more details.

#Usage

Configure your Environment as usual and simply add the DisallowedRawHtmlExtension provided by this package:

use League\CommonMark\Environment\Environment;
use League\CommonMark\Extension\CommonMark\CommonMarkCoreExtension;
use League\CommonMark\Extension\DisallowedRawHtml\DisallowedRawHtmlExtension;
use League\CommonMark\MarkdownConverter;

// Customize the extension's configuration if needed
// Default values are shown below - you can omit this configuration if you're happy with those defaults
// and don't want to customize them
$config = [
    'disallowed_raw_html' => [
        'disallowed_tags' => ['title', 'textarea', 'style', 'xmp', 'iframe', 'noembed', 'noframes', 'script', 'plaintext'],
    ],
];

// Configure the Environment with all the CommonMark parsers/renderers
$environment = new Environment($config);
$environment->addExtension(new CommonMarkCoreExtension());

// Add this extension
$environment->addExtension(new DisallowedRawHtmlExtension());

// Instantiate the converter engine and start converting some Markdown!
$converter = new MarkdownConverter($environment);
echo $converter->convert('I cannot change the page <title>anymore</title>');

#Configuration

This extension can be configured by providing a disallowed_raw_html array with the following nested configuration options. The defaults are shown in the code example above.

#disallowed_tags

An array containing a list of tags that should be escaped.