User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0 Build ID: 20171112125346 Steps to reproduce: I want to close a tab with mouse, I middle click on it Actual results: Usually it closes, but sometimes not. No method to reproduce it, happens on every kind of tab (empty, settings, website). Expected results: Tab closes always

And you are sure that this is not a broken button in your mouse ? I had to replace my mouse 2 days ago just due to this issue.

Since my mouse buttons _always_ works, just not on those tabs, I would think I don't have a broken button. It would be very strange to notice this issue only when I am using Firefox AND closing tabs. Opening tabs in new window alwyays works.

I can second this. I have exactly the same problem - tab not closing on middle click sometimes. I tried to run FF57 in safe mode, but result was the same. Also its not my mouse because I have 2 FF on my PC (52 and 57), and ver52 doent have this problem.

I probably found source of the problem and how to reproduce that. 1. Press middle button on tab. 2. Move cursor a little. 3. Release middle button. 4. In 90% cases tab will stay. Since "middle button" actually mouse wheel and its a liitle bit harder to press it, mouse sometimes moving during press/release process. Above steps works clearly different in <57 versions: tab will be closed despite mouse moving between press an release.

I can confirm that the tab doesn't always close if you release the mouse button while you move the mouse

Regression range https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=47709bd65292f421d98962293f695d6866e65035&tochange=f91c159b317076ac6a6829fd8f58f23b7d6bc3bb I would bet a beer on bug 1349555

FF 58.0.2 still affected What does "fix-optional" mean? I tried to found information in user guide/firefox flags and google but no info there

fix-optional means we could still take a patch, but we aren't going to keep triaging the bug weekly. It's too late to fix this in 59, but we can still take a patch in Nightly. Dão, can you take a look? I'll follow up in email.

This was fixed on firefox 60.0.x but with Update on 61.0.1 the Tabs dont close. Cant be such a big Problem.

(In reply to Chris from comment #9) > This was fixed on firefox 60.0.x but with Update on 61.0.1 the Tabs dont > close. Cant be such a big Problem. You can help shed light on this by finding when exactly this supposedly regressed in 61.

I checked my Update Chronik and now I am confused. Last two Versions are. 61.0 (20180621126525) -> probaby fixed 61.0.1 (20180704003137) -> Tabs don't close I am on "silent update mode" so i don't realize any update. But last Week I have tested - and all Tabs closed. So I'm not really sure, but I think 61.0 don't had this Problem. I only use the middle Mouse to close Tabs, so hope this will be fixed soon. Thanks.

Hi, I reproduced this issue on a lot of versions of Firefox Nightly all the way back to a build from 2018-01-01 and i realized that it might be related to the site and the tabs you opened from that site. I can reproduce this issue 100% of the time by following these steps: 1. Reach www.ign.com (if you have a different country switch to the United States site) 2. Mouse Wheel Click on "News" a few times in order to open a few tabs. 3. Mouse Wheel Click and drag a centimeter or two while still staying in the tab before letting go of the mouse wheel. The "Articles" tab will still remain open. Please note that other tabs will close a lot easier than the "NEWS" tab. Also I tested version 56.0a1 (2017-08-01) and the issue does not occur here so the above mentioned regression range seems correct. After version 56.0a1 (2017-08-01) using my steps I managed to reproduce this issue on every version of Firefox including Release 61. Can you also try reproducing the issue using these steps?