Created attachment 274454 [details]
The drop-down button was where "open with gedit" is shown; releasing the button unintentionally opens the attachment in gedit.

The „open attachment“ drop-down menu has usability issues when it’s located near the bottom of the screen (i.e. when there’s not enough space to the bottom to show the menu). Under these circumstances, the menu will be shown on top of the button, and releasing the click will count as selection. So if you release the button (expecting that the menu will stay open) you unintentionally trigger a menu item. Additionally, the dropdown menu will be too small too display all entries and require scrolling.

It would be better if the menu opened to the top when there’s insufficient space to the bottom, and it should never be rendered on top of the button used to open the menu. If it can only be rendered on top of the button, then releasing the button should not immediately trigger the menu selection.