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Dancer::Plugin::EscapeHTML - Escape HTML entities to avoid XSS vulnerabilities


This plugin provides convenience keywords escape_html and unescape_html which are simply quick shortcuts to encode_entities and decode_entities from HTML::Entities.

    use Dancer::Plugin::EscapeHTML;

    my $encoded = escape_html($some_html);

It also provides optional automatic escaping of all HTML (see below.)


This plugin is intended to provide a quick and simple way to ensure that HTML passed in the tokens hashref to the template is safely escaped (encoded), thereby helping to avoid XSS/cross-site scripting vulnerabilities.

You can encode specific bits of data yourself using the escape_html and unescape_html keywords, or you can enable automatic escaping of all values passed to the template.


When the plugin is loaded, the following keywords are exported to your app:


Encodes HTML entities; shortcut to encode_entities from HTML::Entities


Decodes HTML entities; shortcut to decode_entities from HTML::Entities

Automatic HTML encoding

If desired, you can also enable automatic HTML encoding of all params passed to templates.

If you're using Template Toolkit, you may wish to look instead at Template::Stash::EscapeHTML which takes care of this reliably at the template engine level, and is more widely-used and tested than this module.

To arrange for this plugin to automatically encode HTML entities, enable the automatic_encoding option in your app's config - for instance, add the following to your config.yml:

            automatic_escaping: 1

Now, all values passed to the template will be automatically encoded, so you should be protected from potential XSS vulnerabilities.

Of course, this has the drawback that you cannot provide pre-prepared HTML in template params to be used "as is". You can get round this by using the exclude_pattern option to provide a pattern to match token names which should be exempted from automatic escaping - for example:

            automatic_escaping: 1
            exclude_pattern: '_html$'

The above would exclude token names ending in _html from being escaped.

By default, blessed objects being passed to the template will be left unmolested, as digging around in the internals of the object is probably not wise or desirable. However, if you do want this to be done, set the traverse_objects setting to a true value, and objects will be treated just like any other hashref/arrayref.






David Precious, <davidp at>


Tom Rathborne <tom.rathborne at>


Copyright 2011 David Precious.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See for more information.