There are several vulnerabilities being actively exploited. The vulnerabilities were discovered and seemingly leaked from the Israeli NSO Group. Anyone with this leak can hack you just by knowing your phone number, and we don't know how bad it is!
Especially if you're an activist, or were near any protests recently, or otherwise expect you might be surveiled. Or you're a researcher, academic, etc.
A patch is out. Once a patch is out, people who don't know how the vulnerability works can reverse-engineer it from the patch. Then, it's only useful to the extent that they can find people who have yet to update.
But this time, the details of the hack were published, and little reverse engineering is needed.
TLDR: You should update all your Apple devices as soon as you can.