Hello. Since some time (few months, can't really say when this started happening), the middle mouse button click on a tab stopped working as before. I will describe the expected behavior and how it (still) works on the same computer with a different browser (Chrome): 1. Hover over a tab 2. Middle-click closes a tab 3. Tabs right to the closed one move left 4. Middle-click closes a tab 5. Steps 2-4 may be repeated unless there are no tabs opened 6. Leaving the tabs bar (if any left opened) will now rearrange the remaining tabs (increase their width, etc) Now, here is the not so great behavior I am facing in Firefox: 1. Hover over a tab 2. Middle-click closes a tab 3. Tabs right to the closed one move left '''4. Middle-click rearranges the remaining tabs (increase their width, etc)''' 5. Middle-click closes a tab 6. Steps 2-'''5''' may be repeated unless there are no tabs opened 7. Leaving the tabs bar (if any left opened) will now rearrange the remaining tabs (increase their width, etc), if you have left at last step 3 See, there is this extra step #4 which is really bugging me enough to actually come and ask for a support. I am on Ubuntu 20.04, using latest version of Firefox (to date). Many thanks!