Sorry, I made a mistake during my explanation. I meant Left analog X axis goes right, as you stated.
Anyway the problem is that 3 month ago, when I was using my xBox controler and I pressed right, my character was going right, when pressed left, it was going left, when pressing down, it was going down and when pressing top, it was going top.
3 months later, without touching the code, when I press left, it goes down, when I press right, it goes top, when I press top, it goes right and when I press down, it goes left.
The controls were fine 3 months ago, and today, it seems the X and Y axis got switched without me touching the code at all.
Edit : Ok so I created a new project with a simple platform behavior sprite with right and left detection only. The problem comes from Firefox 31 which inverted the X and Y axis... I tested on chrome and it works fine.
I hope this will be corrected in next version...