Keyboard Auto Pop-up Issue (New issue in Version 43)

After updating Firefox to version 43, Firefox now recognizes when text fields are selected and auto pops-up the virtual on-screen keyboard. The issue is that this breaks several websites and heavily interferes with web browsing (since I use a wireless keyboard and mouse with my tablet, having the virtual keyboard pop-up is useless). I'd much rather have the previous behaviour where I choose to have keyboard pop-up when I click on the taskbar button. Several websites, once visited, have text fields auto-selected which trigger the keyboard to show up. This is very annoying. How can I disable Firefox from having the on-screen keyboard auto pop-up? NOTE: This is a NEW ISSUE in the 43rd version of Firefox, I've installed a vanilla copy of Firefox 42 and it does not have this issue. Once I've updated to 43, the issue appears. (Currently running Windows 8.1)