ads won't open in new tab

hi there, i got another one 😉 i’m using http://wordpress.org/plugins/wp-external-links/ so all external links will open in a new tab. this works nicely for any ads, but not the one inserted in the theme ad managment slots (and hereby handled by this plugin)

example here: http://www.helene-fischer-fans.com

the 300×250 ad in the sidebar will open in a new tab
the 728×90 ad under the navigation opens in _self 🙁

https://wordpress.org/plugins/extended-adrotate-ad-placements/