This bug was filed from the Socorro interface and is report bp-0c248480-0ee0-4f27-a9fb-ab57a0181111. ============================================================= Top 10 frames of crashing thread: 0 xul.dll nsGlobalWindowOuter::SetOpenerWindow dom/base/nsGlobalWindowOuter.cpp:2246 1 xul.dll nsresult nsWindowWatcher::OpenWindowInternal toolkit/components/windowwatcher/nsWindowWatcher.cpp:998 2 xul.dll nsWindowWatcher::OpenWindow2 toolkit/components/windowwatcher/nsWindowWatcher.cpp:413 3 xul.dll nsGlobalWindowOuter::OpenInternal dom/base/nsGlobalWindowOuter.cpp:7141 4 xul.dll nsGlobalWindowInner::Open dom/base/nsGlobalWindowInner.cpp:4074 5 xul.dll static bool mozilla::dom::Window_Binding::open dom/bindings/WindowBinding.cpp:2614 6 xul.dll mozilla::dom::binding_detail::GenericMethod<mozilla::dom::binding_detail::MaybeGlobalThisPolicy, mozilla::dom::binding_detail::ThrowExceptions> dom/bindings/BindingUtils.cpp:3374 7 xul.dll js::InternalCallOrConstruct js/src/vm/Interpreter.cpp:560 8 xul.dll static bool InternalCall js/src/vm/Interpreter.cpp:614 9 xul.dll static bool Interpret js/src/vm/Interpreter.cpp:3461 ============================================================= There is 1 crash in nightly 65 with buildid 20181110100119. In analyzing the backtrace, the regression may have been introduced by patch [1] to fix bug 1502328. [1] https://hg.mozilla.org/mozilla-central/rev?node=d697bd75684d

Yes, this is an assert introduced in bug 1502328. Taking the bug.

Bug 1506852 adds a couple of asserts that should highlight exactly what's going on, but we should also keep in mind that this is a diagnostic assert, so it won't escape nightly, and it has been seen three times in five days, which isn't that much. I've requested access to dumps to be able to look at this deeper.

Marking this as duplicate of Bug 1507168 that actually has a test case. The reason for this asssertion is a window.open happens roughly at the same time as window goes away (for some reason) leaving the newly opened window trying to set its opener to something that is still alive (where alive means being destroyed, but the nsPIDOMWindowOuter* passed to nsGlobalWindowOuter::SetOpenerWindow still pointing to something), but the docshell of that opener has already been torn down.