As far as I know pressing ALT key is the option to reveal menu in the product.

It will act the same till it is removed. There is not much to do.

You can set the ui.key.menuAccessKeyFocuses pref to false on the about:config page to prevent opening the menu when holding down the Alt key. This may require to close and restart Firefox.

• ui.key.menuAccessKeyFocuses = false

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Note that the pref is automatically set when toggling between the autohide and permanently-shown state.

Note that the pref is automatically set when toggling between the autohide and permanently-shown state.

Pavel said

Is there a way to disable popping-up Menu bar by pressing Alt key?

Hello Pavel,

Would you do this please :

Type in the address bar about:config and press Enter (ignore the warning)

Type in the search bar and look for the preference :

ui.key.menuAccessKeyFocuses

and set its value to false

That should do the trick.

Oops, looks like cor-el posted this solution while I was typing my post.