Improper validation of URLs ('Cross-site Scripting') in Wagtail rich text fields

Vulnerability Description

Wagtail is a Django content management system. In affected versions of Wagtail, 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. See referenced GitHub advisory for additional details, including a workaround. 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).

References

• https://github.com/wagtail/wagtail/security/advisories/GHSA-wq5h-f9p5-q7fx
• https://pypi.org/project/wagtail/