This bug was filed from the Socorro interface and is report bp-4cf7889c-4e01-4600-95f1-4e0770180823. ============================================================= Top 10 frames of crashing thread: 0 @0x7fff6370a20a 1 XUL mozilla::recordreplay::RR_mach_msg toolkit/recordreplay/ProcessRedirect.h:119 2 XUL google_breakpad::ReceivePort::WaitForMessage toolkit/crashreporter/google-breakpad/src/common/mac/MachIPC.mm:249 3 XUL google_breakpad::CrashGenerationClient::RequestDumpForException toolkit/crashreporter/breakpad-client/mac/crash_generation/crash_generation_client.cc:77 4 XUL google_breakpad::ExceptionHandler::WriteMinidumpWithException toolkit/crashreporter/breakpad-client/mac/handler/exception_handler.cc:382 5 XUL google_breakpad::ExceptionHandler::WriteForwardedExceptionMinidump toolkit/crashreporter/breakpad-client/mac/handler/exception_handler.cc:651 6 XUL mozilla::recordreplay::child::ReportFatalError toolkit/recordreplay/ipc/ChildIPC.cpp:329 7 XUL RecordReplayInterface_InternalRecordReplayAssert toolkit/recordreplay/ProcessRecordReplay.cpp:474 8 XUL mozilla::recordreplay::RecordReplayAssert mfbt/RecordReplay.h:474 9 XUL mozilla::recordreplay::RR_CFRetain toolkit/recordreplay/ProcessRedirect.h:193 ============================================================= This is showing up in the 8-22 build, which contains the fix for bug 1483365. Interestingly, this does actually contain a RecordReplayError field: Assertion Mismatch: Thread 1 Recorded: CFRelease [62737769,31959] Replayed: CFRetain ### _ZN7mozilla12recordreplayL11RR_CFRetainEm ### _ZN14MacOSFontEntryC2ERK12nsTSubstringIDsEP6CGFontN7mozilla11WeightRangeENS6_12StretchRangeENS6_15SlantStyleRangeEbb ### _ZN22gfxMacPlatformFontList16MakePlatformFontERK12nsTSubstringIDsEN7mozilla11WeightRangeENS4_12StretchRangeENS4_15SlantStyleRangeEPKhj ### _ZN16gfxUserFontEntry16LoadPlatformFontEPKhRj ### _ZN16gfxUserFontEntry24FontDataDownloadCompleteEPKhj8nsresult ### _ZN16nsFontFaceLoader16OnStreamCompleteEP15nsIStreamLoaderP11nsISupports8nsresultjPKh ### _ZN7mozilla3net14nsStreamLoader13OnStopRequestEP10nsIRequestP11nsISupports8nsresult ### _ZN19nsCORSListenerProxy13OnStopRequestEP10nsIRequestP11nsISupports8nsresult ### _ZN7mozilla3net16HttpChannelChild15DoOnStopRequestEP10nsIRequest8nsresultP11nsISupports ### _ZN7mozilla3net16HttpChannelChild13OnStopRequestERK8nsresultRKNS0_20ResourceTimingStructERKNS0_17nsHttpHeaderArrayE ### _ZN7mozilla3net17ChannelEventQueue10FlushQueueEv ### [62737769,31959] Here's another crash report with the same signature: bp-99301fb7-8da8-458b-811e-e74000180823#tab-metadata The RecordReplayError looks different for that report, so maybe it is something else?

The CFRetain crash looks like bug 1479921, which I haven't been able to reproduce yet (it might be specific to 10.13, which I haven't upgraded to yet). The second part looks like it might be fixed by part 3 of bug 1479909, but it's hard to say for sure.