Wagtail: Reflected XSS in dynamic image URL generator view

Impact

A reflected cross-site scripting (XSS) vulnerability exists on the dynamic image URL generator view within the Wagtail admin interface. A user with a limited-permission editor account for the Wagtail admin could craft a URL that, when viewed by a user with higher privileges, could perform actions with that user's credentials. The vulnerability is present for all sites, even if they do not enable the dynamic image serve view. The vulnerability is not exploitable by an ordinary site visitor without access to the Wagtail admin.

Patches

Patched versions have been released as Wagtail 7.3.3 and 7.4.2.

Workarounds

For sites that cannot easily upgrade to a current supported version, the vulnerability can be patched by adding the following code to urls.py URL pattern declarations to override the vulnerable view. This disables the admin dynamic image preview functionality, while the public-facing dynamic image serve view still works.

from django.http import HttpResponseBadRequest
from django.urls import path
from wagtail.admin import urls as wagtailadmin_urls

def disabled_output(request, image_id):
    return HttpResponseBadRequest("", content_type="text/plain")

urlpatterns = [
    # Example where the CMS admin is at /admin/.
    # Add this before the Wagtail admin URLs registration, with the same sub-path.
    path("admin/images//generate_url/output/", disabled_output),
    path("admin/", include(wagtailadmin_urls)),
]