Mozilla (Firefox/Thunderbird) : default application used to open file is sometimes wrong

For a while now in both:

  • Firefox when clicking on an item in the download list
  • Thunderbird when opening an attachment

I've noticed something weird happening: the default application is all wrong.

For those wondering: clicking "Other..." leads to a file browsing window - not very helpful.

This does not happen all the time, and I'm not sure what I did to cause it to start behaving this way.

:arrow_right: Anyone else experiencing this?

For Thunderbird (Screenshot above) it's because there's this weird second entry in the attachments settings. But this is not something I added myself, I'm quite sure of it:

Ubuntu MATE 16.04 LTS up to date as of 2016-07-13

System using English as default language and French as locale.

:arrow_right: Selecting “Delete Action” from the list on the right of the second entry restores correct behavior.