Safari freezes on any form asking for a password

For those having trouble with Safari freezing on any page containing a password form (registration page, password update,...), here is the true solution:

In order to fix it, you must allow keychain storage on icloud: go to configuration > icloud > keychain (“trousseau” for french users), enable it (you might be asked to enable two way authentication for that).

Wait few seconds/minutes for the sync, and that’s it - no more freeze with safari on password forms.

If Keychain was already enabled on your device, then turn it off and back on again. It will force you to put in a passcode, then it will be done and you will be able to sign in to any website quickly again.