Patching vulnerabies in Opera

A Former User

Would someone here be so polite to explain to me, how Opera handles zero-days-exploits in Chromium?
I was told the other day that all Chromium-based browsers fixed the last exploits within a day, but that it took Opera almost 12 days to do that.
This sounds a bit worrying as we users are relying on secure and quickly patched software. I haven't found anything about that issue in the general section. So maybe there are reasons for the delay.

I've also seen that Opera also is one of these browsers that keep updating to the newest Chromium version later than others.

I really like using Opera, I have to confess. Its clean design and some of the handy features are really standing out. And I make use a lot of them. But security is of course so basic that it even trumps design and workflow.

Thank you very much in advance.