I'm getting several invalid requests from a "BingPreview" user agent. The complete user agent header is:
Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/534+ (KHTML, like Gecko) BingPreview/1.0b
The invalid requests seem to come from a bug in the HTML parser in the crawler, which ends up generating invalid URLs.
Is this user agent legit, really related to Bing? Or is it yet another fraud?