It is explained here https://grapheneos.org/usage#web-browsing
They don’t explicitly mention Firefox but:
"Chromium-based browsers like Vanadium provide the strongest sandbox implementation, leagues ahead of the alternatives. "
and
"Chromium has decent exploit mitigations, unlike the available alternatives. "
Since I myself lack the knowledge and skills to judge this, I have to trust the word of the developers.
Edit, correction. They do mention Firefox
“Avoid Gecko-based browsers like Firefox as they’re currently much more vulnerable to exploitation and inherently add a huge amount of attack surface.”
















I feel like people lately go a bit overboard when it’s about protecting their “data”.
As far as I see all it does is just send one single number that shows that there is someone using this specific operation system and it does not include any personal or unique to the user information.
In my opinion this does not even qualify as “my data”