Crash report: https://crash-stats.mozilla.org/report/index/95094381-c178-4856-a205-0ebdf0210225

Reason: EXCEPTION_ACCESS_VIOLATION_WRITE

Top 10 frames of crashing thread:

0 ntdll.dll RtlEnterCriticalSection 
1 mozglue.dll static Allocator<MozJemallocBase>::free memory/build/malloc_decls.h:54
2 xul.dll FinalizeArenas js/src/gc/GC.cpp:593
3 xul.dll js::gc::BackgroundSweepTask::run js/src/gc/GC.cpp:3503
4 xul.dll js::GCParallelTask::runTask js/src/gc/GCParallelTask.cpp:156
5 xul.dll js::GCParallelTask::runHelperThreadTask js/src/gc/GCParallelTask.cpp:143
6 xul.dll static js::HelperThread::ThreadMain js/src/vm/HelperThreads.cpp:2342
7 xul.dll static js::detail::ThreadTrampoline<void  js/src/threading/Thread.h:205
8 ucrtbase.dll thread_start<unsigned int , 1> 
9 b_scqdqe.dll b_scqdqe.dll@0x17033 

Affected versions

• Fx 87.0b2

Affected platforms

• Windows 10

Steps to reproduce

1. On a dirty profile open a youtube video (eg. https://www.youtube.com/watch?v=7KSWQAceo6g) and let it play in the background
2. Open several Alexa top sites in different tabs

Actual result

• Youtube tab crashes

Regression range

• This is a one time crash on my side, it looks like I can’t trigger it again

Additional notes

• The video played normally after tab restore

Closing because no crashes reported for 12 weeks.