The following code:

bindings.addBinding('TAB', hterm.Keyboard.KeyActions.PASS);

will work correctly in Chrome but not in Firefox. This is because Firefox seems to trigger both a Keydown and Keypress event while Chrome only fires a Keydown event.

It is not possible to reenable tab-based navigation in Firefox.

Other quirks can be seen as well with bindings such as:
bindings.addBinding('TAB', hterm.Keyboard.KeyActions.PASS);
Expected: Mute tab (pass command to Firefox)
Actual result: Type m in the terminal.

What is the expected result?
- Tab key is sent to the browser and the next element gains focus.

What happens instead?
- Nothing, as the event is stopped in the keypress handler.

This should be relatively easy to fix, simply filtering out the extra Firefox events in the keypress handler.