A Bing Community thread reports from one webmaster that someone is masking MSNBot around as a browser, either Internet Explorer or Mozilla Firefox. Here are the reported IPs and UserAgent’s being reporting by this webmaster:

This is not the first time Microsoft Bing has been accused of masking their bots as browser useragents. We had a similar report back in September where MSNBot was using Mozilla by way of UserAgent.

Brett Yount, Bing’s representative, said, “Could you send this information to [email protected] and I will have the crawling team investigate?”

So currently, this is not confirmed, but it is weird.

Forum discussion at Bing Community.