Researchers have been analysing the patch and have been able to trigger the crash within the iOS JPEG lossless decompression within RawCamera.bundle. Some git repositories with the results of their analysis have been made public here and here.
According to Apple, this issue has been "exploited in an extremely sophisticated attack against specific targeted individuals". A vulnerability of this nature takes significant resources to develop. As such, this is extremely valuable to threat actors where some vulnerability brokers would pay up to $15 million for a working proof-of-concept for this type of attack. Therefore we can assume widespread exploitation has not happened, but with the progress researchers have been making it will only be a matter of time before that happens. Patches should be applied immediately.