Wagtail regular expression denial-of-service via search query parsing

Wagtail is an open source content management system built on Django. A bug in Wagtail's `parse_query_string` would result in it taking a long time to process suitably crafted inputs. When used to parse sufficiently long strings of characters without a space, `parse_query_string` would take an unexpectedly large amount of time to process, resulting in a denial of service. In an initial Wagtail installation, the vulnerability can be exploited by any Wagtail admin user. It cannot be exploited by end users. If your Wagtail site has a custom search implementation which uses `parse_query_string`, it may be exploitable by other users (e.g. unauthenticated users). Patched versions have been released as Wagtail 5.2.6, 6.0.6 and 6.1.3.