Potential Observable Timing Discrepancy in Wagtail

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.