Abrupt closing of graphical session after various user actions on systems with Intel graphic card

Problem: MATE, Openbox Session is closing, blank screen and falling back to login screen

Other symptoms: Every crash produces a file in / called something like core.1428141; these are about 150MB of text each.

Solution:

There are problems with the default configuration on xorg.
The solution is to create a file called 20-intel.conf and upload it to the /etc/X11/xorg.conf.d folder:

In the Terminal (Ctrl+Alt+T) paste this command:

sudo nano /etc/X11/xorg.conf.d/20-intel.conf

And after paste this:

Section "Device"
  Identifier "Intel Graphics"
  Driver "Intel"
  Option "TearFree" "true"
EndSection

Now press Ctrl+Shift+X and after press Y to Yes on "Save modified buffer?" and press Enter to save the file.

And reboot your computer!

Sources:

https://trisquel.info/es/forum/x11-close-session-when-opening-file-or-browsing-web
https://trisquel.info/en/forum/certain-tasks-make-screen-go-black-blinking-underscore-then-i-have-log-again-0