First reported here http://forums.mozillazine.org/viewtopic.php?p=14770533#p14770533 and uBlockOrigin/uAssets#759

Describe the issue

uBlock Origin 1.14.14
SeaMonkey 2.49.1

Steps to reproduce -

1. add this filter

   ||adobe.com^$popup

2. visit http://get.adobe.com/flashplayer/about/

3. in the right sidebar of the page, left-click the link "Games".

Result: Link opens in a new tab, as expected, but the original tab is closed. Logger reports this -

||adobe.com^$popup   --   popunder   http://get.adobe.com/flashplayer/about/