It's currently #3 top crasher in today's build and first appeared in 16.0a1/20120706075126. If the regression range has a meaning for this kind of random bugs, it would be: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=4b1249ae1906&tochange=a8f682801a6d Signature nsStyleSet::GetContext(nsStyleContext*, nsRuleNode*, nsRuleNode*, bool, bool, nsIAtom*, nsCSSPseudoElements::Type, bool, mozilla::dom::Element*) More Reports Search UUID 2cdb6463-b237-407e-9e9f-38bbc2120707 Date Processed 2012-07-07 03:56:35 Uptime 4378 Last Crash 4.0 weeks before submission Install Age 1.2 hours since version was first installed. Install Time 2012-07-07 02:43:22 Product Firefox Version 16.0a1 Build ID 20120706075126 Release Channel nightly OS Windows NT OS Version 6.1.7601 Service Pack 1 Build Architecture x86 Build Architecture Info AuthenticAMD family 20 model 2 stepping 0 Crash Reason EXCEPTION_ACCESS_VIOLATION_EXEC Crash Address 0xd App Notes AdapterVendorID: 0x1002, AdapterDeviceID: 0x9807, AdapterSubsysID: 05981025, AdapterDriverVersion: 8.951.0.0 D3D10 Layers? D3D10 Layers- D3D9 Layers? D3D9 Layers- EMCheckCompatibility True Adapter Vendor ID 0x1002 Adapter Device ID 0x9807 Total Virtual Memory 4294836224 Available Virtual Memory 3789332480 System Memory Use Percentage 50 Available Page File 5880213504 Available Physical Memory 1979305984 Frame Module Signature Source 0 @0xd 1 xul.dll nsStyleSet::GetContext layout/style/nsStyleSet.cpp:585 2 xul.dll nsFrameManager::ReResolveStyleContext layout/base/nsFrameManager.cpp:1206 3 @0x13ce60ff 4 xul.dll xul.dll@0x1294cf 5 xul.dll mozilla::css::RestyleTracker::DoProcessRestyles layout/base/RestyleTracker.cpp:209 6 xul.dll nsCSSFrameConstructor::ProcessPendingRestyles layout/base/nsCSSFrameConstructor.cpp:11913 7 xul.dll PresShell::FlushPendingNotifications layout/base/nsPresShell.cpp:3813 8 xul.dll ExternalResourceTraverser content/base/src/nsDocument.cpp:760 9 xul.dll nsRefreshDriver::Notify layout/base/nsRefreshDriver.cpp:375 10 nspr4.dll nspr4.dll@0x8caf 11 shell32.dll shell32.dll@0xae1b27 12 xul.dll nsThread::ProcessNextEvent xpcom/threads/nsThread.cpp:624 13 xul.dll mozilla::ipc::MessagePump::Run ipc/glue/MessagePump.cpp:82 14 xul.dll MessageLoop::RunHandler ipc/chromium/src/base/message_loop.cc:201 15 xul.dll _SEH_epilog4 16 xul.dll MessageLoop::Run ipc/chromium/src/base/message_loop.cc:175 17 xul.dll nsBaseAppShell::Run widget/xpwidgets/nsBaseAppShell.cpp:163 18 xul.dll nsAppShell::Run widget/windows/nsAppShell.cpp:232 19 xul.dll nsAppStartup::Run toolkit/components/startup/nsAppStartup.cpp:256 20 xul.dll XREMain::XRE_mainRun toolkit/xre/nsAppRunner.cpp:3787 21 xul.dll XREMain::XRE_main toolkit/xre/nsAppRunner.cpp:3864 22 xul.dll XRE_main toolkit/xre/nsAppRunner.cpp:3940 ... More reports at: https://crash-stats.mozilla.com/report/list?signature=nsStyleSet%3A%3AGetContext%28nsStyleContext*%2C+nsRuleNode*%2C+nsRuleNode*%2C+bool%2C+bool%2C+nsIAtom*%2C+nsCSSPseudoElements%3A%3AType%2C+bool%2C+mozilla%3A%3Adom%3A%3AElement*%29

As usual, those crashes are gone in the next build.

Crash volume for signature 'nsStyleSet::GetContext': - nightly (version 51): 0 crashes from 2016-08-01. - aurora (version 50): 0 crashes from 2016-08-01. - beta (version 49): 94 crashes from 2016-08-02. - release (version 48): 10 crashes from 2016-07-25. - esr (version 45): 31 crashes from 2016-05-02. Crash volume on the last weeks (Week N is from 08-22 to 08-28): W. N-1 W. N-2 W. N-3 - nightly 0 0 0 - aurora 0 0 0 - beta 29 35 6 - release 1 8 0 - esr 3 3 2 Affected platform: Windows Crash rank on the last 7 days: Browser Content Plugin - nightly - aurora - beta #579 #338 - release #8654 - esr #1065

Crash volume for signature 'nsStyleSet::GetContext': - nightly (version 52): 0 crashes from 2016-09-19. - aurora (version 51): 0 crashes from 2016-09-19. - beta (version 50): 9 crashes from 2016-09-20. - release (version 49): 370 crashes from 2016-09-05. - esr (version 45): 39 crashes from 2016-07-25. Crash volume on the last weeks (Week N is from 10-17 to 10-23): W. N-1 W. N-2 W. N-3 W. N-4 - nightly 0 0 0 0 - aurora 0 0 0 0 - beta 5 0 2 2 - release 93 116 103 14 - esr 4 2 6 1 Affected platforms: Windows, Linux Crash rank on the last 7 days: Browser Content Plugin - nightly - aurora - beta #14234 #1772 - release #630 #471 - esr #1706