The recently released Liferay 7.3 introduced the concept of Applications Menu (See
LPS-119736 for details).
The shortcut key combination to toggle the Menu is CTRL+Shift+M. This shortcut, on the other hand, is also available natively in Firefox (Open responsive mode) and Chrome/Edge Chromium (Open User Profile Management window) browsers.
Based on the above, on Firefox and Chrome, CTRL+Shift+M leads to different results whether being logged into Liferay 7.3 or not.
A different key combination to open Applications Menu on Liferay 7.3 should be conceived, so that there is no overlap with native browser's shortcuts.