User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:46.0) Gecko/20100101 Firefox/46.0 Build ID: 20160425115534 Steps to reproduce: I tried to selected file with the file picker to a smb share (mounted by thunar), for example to : - save a web page - save attachment on mail page - ... Tested on OS : Xubuntu 14.04 64b and Xubuntu 16.04 64b Actual results: The file picker doesn't show anymore mounted folder. Expected results: In previous version of Firefox the file picker was able to select mounted folder. I guess it's linked with gtk update.