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Embedding HTML in Django Messages

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Embedding HTML in Django Messages

· Web Dev Zone ·
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Deploying code to production can be filled with uncertainty. Reduce the risks, and deploy earlier and more often. Download this free guide to learn more. Brought to you in partnership with Rollbar.

Problem

You want to embed HTML within a message using Django's messages framework.

This is a reasonably common requirement - for instance, it's common to want to include a link within the message, perhaps pointing the user towards a sign-in or registration page.

This problem exists as of Django 1.4 but may be solved within the framework in later versions.

Solution

Use the extra_tags keyword argument to pass a flag indicating that the message is safe for rendering without escaping. For example:

from django.contrib import messages

def some_view(request):
    ...
    messages.success(request,
                     'Here is a <a href="/">link</a>.',
                     extra_tags='safe')

 Then use some simple template logic to determine whether to use the safe filter:

<ul>
    {% for message in messages %}
    <li class="{{ message.tags }}">
        {% if 'safe' in message.tags %}
            {{ message|safe }}
        {% else %}
            {{ message }}
        {% endif %}
    </li>
    {% endfor %}
</ul>

Discussion

It's tempting to use the safe filter for all messages but this opens up a XSS security hole if you are not careful as it's easy to include user input verbatim in the message. For instance:

from django.contrib import messages

def some_view(request):
    code = request.GET['code']
    ...
    messages.success(request, "'%s' is not valid voucher code" % code)

 leads to an XSS hole if the safe filter is used on all messages as the contents of request.GET['code'] cannot be trusted. It's better to explicitly indicate which messages can be safely rendered without escaping.

Deploying code to production can be filled with uncertainty. Reduce the risks, and deploy earlier and more often. Download this free guide to learn more. Brought to you in partnership with Rollbar.

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