In Wagtail before versions 2.7.4 and 2.9.3, when a form page type is made available to Wagtail editors through the `wagtail.contrib.forms` app, and the page template is built using Django's standard form rendering helpers such as form.as_p, any HTML tags used within a form field's help text will be rendered unescaped in the page. Allowing HTML within help text is an intentional design decision by Django; however, as a matter of policy Wagtail does not allow editors to insert arbitrary HTML by default, as this could potentially be used to carry out cross-site scripting attacks, including privilege escalation. This functionality should therefore not have been made available to editor-level users. The vulnerability is not exploitable by an ordinary site visitor without access to the Wagtail admin. Patched versions have been released as Wagtail 2.7.4 (for the LTS 2.7 branch) and Wagtail 2.9.3 (for the current 2.9 branch). In these versions, help text will be escaped to prevent the inclusion of HTML tags. Site owners who wish to re-enable the use of HTML within help text (and are willing to accept the risk of this being exploited by editors) may set WAGTAILFORMS_HELP_TEXT_ALLOW_HTML = True in their configuration settings. Site owners who are unable to upgrade to the new versions can secure their form page templates by rendering forms field-by-field as per Django's documentation, but omitting the |safe filter when outputting the help text.
In Wagtail before versions 2.7.3 and 2.8.2, a potential timing attack exists on pages or documents that have been protected with a shared password through Wagtail's "Privacy" controls. This password check is performed through a character-by-character string comparison, and so an attacker who is able to measure the time taken by this check to a high degree of accuracy could potentially use timing differences to gain knowledge of the password. This is [understood to be feasible on a local network, but not on the public internet](https://groups.google.com/d/msg/django-developers/iAaq0pvHXuA/fpUuwjK3i2wJ).
Privacy settings that restrict access to pages/documents on a per-user or per-group basis (as opposed to a shared password) are unaffected by this vulnerability.
This has been patched in 2.7.3, 2.8.2, 2.9.
In Wagtail before versions 2.8.1 and 2.7.2, a cross-site scripting (XSS) vulnerability exists on the page revision
comparison view within the Wagtail admin interface. A user with a limited-permission editor account for the Wagtail
admin could potentially craft a page revision history that, when viewed by a user with higher privileges, could perform
actions with that user's credentials. The vulnerability is not exploitable by an ordinary site visitor without access to
the Wagtail admin.
Patched versions have been released as Wagtail 2.7.2 (for the LTS 2.7 branch) and Wagtail 2.8.1 (for the current 2.8 branch).