Border on pop-up menus is too dark

[YarnSphere]

This wasn't an issue before but, since one of the latest releases, the border colour of the pop-up menus (e.g. bookmarks menu, settings menu, downloads menu) appears to be too dark.

Downloads menu (border is black, when it should be grey):

I am using Firefox 45.0.2, theme version 45.1.

[ghost]

Works on my machine.

[YarnSphere]

The same happens on a friend's computer, but I will try to disable as much stuff as possible and try to isolate the problem. But I still think this theme is at fault.

[dyskette]

Which gtk version are you using? Because firefox right now has issues with the new gtk 3.20 which shows black borders on several items.

https://bugzilla.mozilla.org/show_bug.cgi?id=1266914

[YarnSphere]

I'm using GTK version 3.20.3.
You're right, just changed to the default Firefox theme and the issue is still visible; it does seem to be a GTK problem.

I'll keep the issue open until the GTK issue is solved.
If someone in charge wants to close this, please do it.