When using Firefox I have troubles with the use of Alt-Gr inside an open menu window (address bar, search bar, addon popup).
This is particularly annoying since, for instance, when using LastPass I cannot enter my email because the window gets closed as soon as I press Alt-Gr (I need it to type the @ sign).
I tried Safe Mode as well as previous Firefox versions, the problem doesn't fix.
The issue came out after updating some package (apt-get upgrade) I'm using Ubuntu 16.04, (with a Spanish keyboard layout)
How can I fix it?