Crash report: https://crash-stats.mozilla.org/report/index/6a0ec4f1-0286-49e1-a72b-b93e20230514

Reason: EXC_GUARD / GUARD_TYPE_MACH_PORT / 0x2000000300000000 / 0x0000000000000000

Top 10 frames of crashing thread:

0  libsystem_kernel.dylib  mach_msg2_trap  
1  libsystem_kernel.dylib  mach_msg2_internal  
2  libsystem_kernel.dylib  mach_msg_overwrite  
3  libsystem_kernel.dylib  mach_msg  
4  HIServices  _XMIGPostNotification  
5  HIServices  _AXUIElementPostNotificationWithInfo  
6  AppKit  _NSAccessibilityNotifyWithAXElement  
7  AppKit  _NSAccessibilityNotify  
8  AppKit  NSAccessibilityPostNotificationForObservedElementWithUserInfo  
9  AppKit  -[NSWindow _reallyDoOrderWindowAboveOrBelow:]  

Not a super huge volume on these. It looks like it is accessibility related.

This older crash includes a url and the comment "page down key" so maybe that will help.

Weird. This is indeed a11y related, but our a11y engine doesn't seem to be involved. This looks like the a11y object related to the widget itself, which we don't really control apart from overriding some methods.

Eitan, any ideas here?

I don't know if they're related, but there are lots of crashes with XMIG in the proto signature. (To eliminate the huge numbers of crashes on the oldest versions of macOS, I've confined my search to macOS 11 and above.) Most of these seem to involve accessibility, though only at the OS level. The MIG indicates Mach RPC.

https://crash-stats.mozilla.org/search/?proto_signature=~XMIG&platform_version=%21%5E10.&platform=Mac%20OS%20X&date=%3E%3D2023-03-19T20%3A54%3A00.000Z&date=%3C2023-06-19T20%3A54%3A00.000Z&_facets=signature&_facets=platform_version&_facets=proto_signature&_facets=cpu_arch&_facets=address&_sort=-date&_columns=date&_columns=signature&_columns=product&_columns=version&_columns=build_id&_columns=platform#facet-signature

Yeah, that all looks internal to AppKit. If we are at fault anywhere is might be in the widget code and have something to do with resizing or moving the window perhaps? Would be cool to try to reproduce but I don't have a current MacOS build.