I wanted to share a crash report but before I did I inspected it once more in detail (with 3rd party editor rather than Xcode) and could see some information that are not included when inspecting from Xcode Crashes view:
[...]
Exception Note: EXC_CORPSE_NOTIFY
Termination Reason: SIGNAL 11 Segmentation fault: 11
Terminating Process: exc handler [43798]
Triggered by Thread: 10
[...]
So what's interesting here is that this is actually not crashing in JavaScripCore but it's a segmentation fault (The way the crash report is shown in Xcode is misleading).
We used to get a "segmentation fault: 11" every time when implementing the async/ await API of WKScriptMessageHandlerWithReply with Xcode 13 as I stated here.
It seemed to be resolved as of Xcode 14, but now it simply happens only occasionally (We're unable to reproduce but our users are).
So my best guess for now is that one shouldn't use the async variant of the WKScriptMessageHandlerWithReply API but wait for to properly fix it.