Firefox bug on LocalStorage (i.e. idp.storage.htmlLocalStorage=true)

[Takeshi NISHIMURA]

If you have a trouble with Firefox 61.0/61.0.1 and with Shibboleth IdP configuration idp.storage.htmlLocalStorage=true, it may be caused by Firefox bug.

I found LocalStorage provides out of sync data (stale or empty) if:
1. multi processes (e10s) used
and
2. cookie preference "Keep until: I close Firefox" is selected

This will cause SLO propagation failure and stateless clustering failure.

Additionally, it is also broken in private browsing windows of Firefox, so you should avoid it when you have any trouble with LocalStorage.

I've tested Firefox 61.0 and 61.0.1 and both are affected. Other versions and browsers are not tested.

Best regards,
Takeshi