Firefox password field focus bug

This extension contains a popup with a single password input field set to autofocus.

Why

When a password field is focused Firefox automatically closes the popup.

Where

This issue is reproducable on Ubuntu 18.04 LTS using Firefox version(s):

• Firefox Quantum 60.0 (64-bit)
• Firefox Nightly 62.0a1 (2018-05-16) (64-bit)

This issue is not reproducable on Windows 10 using Firefox version(s):

• Firefox Quantum 60.0.1 (64-bit)

This issue is not reproducable on macOS 10.13.4 using Firefox version(s):

• Firefox Quantum 60.0.1 (64-bit)
• Firefox Nightly 62.0a1 (2018-05-16) (64-bit)

How to test

1. Clone this repo
2. Open about:debugging
3. Enable add-on debugging
4. Click Load Temporary Add-on and select the cloned manifest.json
5. Click the newly added extension in your toolbar.

Expect results

The popup should open and focus the password field, allowing users to input a password.

Actual results

One of two things generally happen:

1. The popup never opens.
2. The popup opens but doesn't allow input or focus of the password field and then closes automatically.

Taking it a step further

Disabling ui.popup.disable_autohide in about:config allows the popup to stay open long enough for a user to manually focus the password field. Once focused the password field appears to accept input normally. However, this is clearly not a viable workaround to this bug.