Hi kaa_aziz , Thank you for reporting this, can you provide a little more details where you are downloading and how you are 'extracting' the files when you updated?

Thank you!

It is possible that Anti-Virus software is causing problems. Try to disable Anti-Virus software temporarily to see if that makes a difference.

Hi, I downloaded the full package https://download-installer.cdn.mozilla.net/pub/firefox/releases/42.0/win32/fr/Firefox%20Setup%2042.0.exe . after that I had to extract the .exe file to a folder under the name of 'Firefox Setup 42.0", and I installed the setup.exe contained in this folder.