According to Review Geek, DuckDuckGo signed a confidential search agreement with Microsoft which means that it does not block all Volish trackers.
DuckDuckGo only acknowledged this 'privacy hole' after it was discovered by a security researcher @thezedwards.
The researcher found that the mobile DuckDuckGo browser does not block Microsoft trackers on third-party websites, such as Facebook-owned Workplace.com.
DuckDuckGo CEO Gabriel Weinberg rushed to Twitter to spin the news saying that Microsoft cannot see what you search in DuckDuckGo, and the DuckDuckGo browser blocks all Microsoft cookies.
But if you visit a website that contains Microsoft's trackers, then your data is exposed to services like Bing and LinkedIn. This is the result of DuckDuckGo's "search syndication agreement" with Microsoft.
So basically to take search information from Bing, the privacy experts at DuckDuckGo had to poke holes in their browser's security system.
DuckDuckGo has not explained how Microsoft uses data from third-party trackers. Technically it is possible for Vole to build targeted ad profiles based on your web activity in DuckDuckGo. Unfortunately, no one can reassure anyone because DuckDuckGo signed an NDA.
Gabriel Weinberg says that DuckDuckGo is "working tirelessly behind the scenes" to improve its deal with Microsoft. Additionally, he expects DuckDuckGo to "include more third-party Microsoft protection" in a future update.