Bing Search is testing an open links in new tab toggle feature directly at the top of its search results page. Frank Sandtmann shared this with me via email yesterday and I was able to replicate it. But not everyone is seeing it, so it does seem like a test.
Here is a GIF of it in action (click it to enlarge):
I personally do not like this and rather it be hidden inside the search settings like it is now both on Bing and Google. But I guess it is always good to test things to see if searchers gain any benefit from the placement there.
Forum discussion at Twitter.