1770433 - Dordle game settings are lost when enabling dFPI

Status: RESOLVED WONTFIX

(Core :: Privacy: Anti-Tracking, defect)

Description

[Emma Zühlcke [:emz]]

https://zaratustra.itch.io/dordle stores stats and settings in localStorage. Since this storage is managed by a third-party https://v6p9d9t4.ssl.hwcdn.net it will be partitioned with dFPI enabled. That means if a user used the application with dFPI disabled and then enables it, the non-partitioned storage is no longer accessible by the app.

User report here: https://itch.io/t/2121197/new-firefox-total-cookie-protection-option-breaks-dordle

STR:

1. Disable dFPI / TCP by setting network.cookie.cookieBehavior to 4.
2. Go to https://zaratustra.itch.io/dordle
3. Open settings via the icon in the top right
4. Enable dark mode
5. Reload the page, dark mode is still applied
6. Enable dFPI / TCP by setting network.cookie.cookieBehavior to 4.
7. Reload the page

Expected result:
Settings persisted, dark mode is still applied

Actual result:
Settings are lost, app is back to light mode.

Comment 1

[Tim Huang[:timhuang] [PTO 10/23 ~ 10/28]]

It's because we switch third-party storage from an unpartitioned one to a partitioned one. So, it would look like the setting loses. We don't have a good solution for this kind of breakage currently. The easiest workaround would be to change the settings again after TCP is on. Fortunately, this will only happen if the setting is stored in a third-party storage/cookies.