I don't think a website has access to your autocomplete unless you select one of them.

Google has access when completing your query or wherever that autocomplete goes.

Firefox's autocomplete implementation doesn't insert values until the user sets focus on the input element, so Firefox wasn't vulnerable to the "sniff user info by autocompleting hidden forms" problem that Chrome was.

You can disable search engine suggestions in the Firefox Search preferences, if that's what you're worried about?

I am not worried about anything I was just pointing out that there is still a potential problem. I understand that for knowledgeable users like average joe on hacker news is probably common sense to disable such features if he wants "full privacy".

Anyways; it's not safe by default which should preferably be.

Firefox can autofill password fields if you choose to remember them yeah. There is a platform bug filed for making these container specific or choosing not to auto populate when they were saved in a container.

The test pilot experiment is really to help us to figure out how people are using containers.

Neither location bar autocomplete nor form field autocomplete are separated by userContextId ... yet. See https://wiki.mozilla.org/Security/Contextual_Identity_Projec... for details.