You should modify the firefox profile parameters:
profile = webdriver.FirefoxProfile()
profile.set_preference("browser.link.open_newwindow", 3)
profile.set_preference("browser.link.open_newwindow.restriction", 0)
driver = webdriver.Firefox(firefox_profile=profile)
if this methode does not work, you can set perference using firefox Options:
from selenium.webdriver.firefox.options import Options
opts = Options()
opts.set_preference("browser.link.open_newwindow.restriction", 0)
opts.set_preference("browser.link.open_newwindow", 3)
driver = webdriver.Firefox(firefox_options=opts)
(A) browser.link.open_newwindow - for links in Firefox tabs :
3 : divert new window to a new tab (default)
2 : allow link to open a new window
1 : force new window into same tab
(B) browser.link.open_newwindow.restriction - for links in Firefox tabs
0 : apply the setting under (A) to ALL new windows (even script windows)
2 : apply the setting under (A) to normal windows, but NOT to script windows
with features (default)
1 : override the setting under (A) and always use new windows