Puntuado con 2 de 5 estrellas

In the recent weeks I have been experiencing a weird bug with this search engine and Firefox. If I go and search for something, anything really and go to a link in the search results, sometimes the resulting page opens in a new tab (which is good) but sometimes it opens a new Window. (Which I hate)
I don't seem to have this problem on any other searh engine I have tried such as Google or Bing and this issue is present on latest FF in both Windows 10 and Manjaro linux 17.1.1