Impact
When saving the contents of a rich text field in the admin interface, Wagtail does not apply server-side checks to ensure that link URLs use a valid protocol. A malicious user with access to the admin interface could thus craft a POST request to publish content with javascript: URLs containing arbitrary code. The vulnerability is not exploitable by an ordinary site visitor without access to the Wagtail admin.
Patches
Patched versions have been released as Wagtail 2.11.7 (for the LTS 2.11 branch) and Wagtail 2.12.4 (for the current 2.12 branch).
Workarounds
For sites that cannot easily upgrade to a current supported version, the vulnerability can be patched by adding the following code to a wagtail_hooks.py module in any installed app:
from draftjs_exporter.dom import DOM
from wagtail.admin.rich_text.converters.html_to_contentstate import ExternalLinkElementHandler, PageLinkElementHandler
from wagtail.core import hooks
from wagtail.core.whitelist import check_url
def link_entity(props):
id_ = props.get('id')
link_props = {}
if id_ is not None:
link_props['linktype'] = 'page'
link_props['id'] = id_
else:
link_props['href'] = check_url(props.get('url'))
return DOM.create_element('a', link_props, props['children'])
@hooks.register('register_rich_text_features', order=1)
def register_link(features):
features.register_converter_rule('contentstate', 'link', {
'from_database_format': {
'a[href]': ExternalLinkElementHandler('LINK'),
'a[linktype="page"]': PageLinkElementHandler('LINK'),
},
'to_database_format': {
'entity_decorators': {'LINK': link_entity}
}
})Acknowledgements
Many thanks to Kevin Breen for reporting this issue.
For more information
If you have any questions or comments about this advisory:
References
kevthehermit Analyst
gasman Analyst
tdunlap607 Analyst
Impact
When saving the contents of a rich text field in the admin interface, Wagtail does not apply server-side checks to ensure that link URLs use a valid protocol. A malicious user with access to the admin interface could thus craft a POST request to publish content with
javascript:URLs containing arbitrary code. The vulnerability is not exploitable by an ordinary site visitor without access to the Wagtail admin.Patches
Patched versions have been released as Wagtail 2.11.7 (for the LTS 2.11 branch) and Wagtail 2.12.4 (for the current 2.12 branch).
Workarounds
For sites that cannot easily upgrade to a current supported version, the vulnerability can be patched by adding the following code to a
wagtail_hooks.pymodule in any installed app:Acknowledgements
Many thanks to Kevin Breen for reporting this issue.
For more information
If you have any questions or comments about this advisory:
0x6ba1e1a86e0f8ce8)References