Of course there are unreleased 0-days, but you can’t do anything about it. Most of them are even kept secret by companies that sell spy software. However, public 0-days are way more dangerous because they are being exploited actively.
Using a different browser until a particular issue is fixed when you are e.g. a journalist still helps with getting hacked.
0-days that we know of
There definitely are 0-days in every major browser engines.
As a matter of fact, Mozilla is probably working on a 0-day breach that haven’t been published by security watchdogs yet.
In the meantime, that particular WebKit breach has already been patched.
There’s no point skipping places when everything is on fire. The only thing you can do is going where it’s safer on average and stay there.
Of course there are unreleased 0-days, but you can’t do anything about it. Most of them are even kept secret by companies that sell spy software. However, public 0-days are way more dangerous because they are being exploited actively.
Using a different browser until a particular issue is fixed when you are e.g. a journalist still helps with getting hacked.