Starting in Firefox 53, Conkeror will crash when links like this are clicked:

<a href="#" target="foo">crashes</a>

This link does not crash:

<a href="#" target="foo" rel="noopener" >doesn't crash<a>

And if the second link is clicked before the first link, the first link will not crash.

Here is a backtrace from a crash:

  #0  0x00007fffe9ed179f in nsGlobalWindow::SetOpenerWindow(nsPIDOMWindowOuter*, bool) [clone .cold.401]
() from /home/scott/src/firefox/dev/libxul.so
#1  0x00007fffec2010ef in nsWindowWatcher::ReadyOpenedDocShellItem(nsIDocShellTreeItem*,
nsPIDOMWindowOuter*, bool, bool, mozIDOMWindowProxy**) ()
   from /home/scott/src/firefox/dev/libxul.so
#2  0x00007fffec1ff0c0 in nsWindowWatcher::OpenWindowInternal(mozIDOMWindowProxy*, char const*, char
const*, char const*, bool, bool, bool, nsIArray*, bool, bool, nsIDocShellLoadInfo*, mozIDOMWindowProxy**) ()
   from /home/scott/src/firefox/dev/libxul.so
#3  0x00007fffeb2adf3c in nsWindowWatcher::OpenWindow2(mozIDOMWindowProxy*, char const*, char const*,
char const*, bool, bool, bool, nsISupports*, bool, bool, nsIDocShellLoadInfo*, mozIDOMWindowProxy**)
[clone .cold.96] ()
   from /home/scott/src/firefox/dev/libxul.so
#4  0x00007fffe9ed4867 in nsGlobalWindow::OpenInternal(nsAString_internal const&, nsAString_internal
const&, nsAString_internal const&, bool, bool, bool, bool, bool, nsIArray*, nsISupports*,
nsIDocShellLoadInfo*, bool, nsPIDOMWindowOuter**) [clone .cold.510] () from
/home/scott/src/firefox/dev/libxul.so
#5  0x00007fffe9ee07bc in nsGlobalWindow::OpenNoNavigate(nsAString_internal const&, nsAString_internal
const&, nsAString_internal const&, nsPIDOMWindowOuter**) ()