Project Zero Finds Security flaw on Edge

The Google Project Zero team strives to detect defects in software developed by the company or other companies. Recently, they detected security vulnerabilities in Microsoft Edge. Security breaches were classified as "medium" and were revealed by Google to Microsoft in November 2017. Subsequently, Microsoft received the 90-day standard to fix the problem before Google made the report public, but the giant the software did not do it, solve the problem even after a prolonged trial period of 14 days. As a result, the problem is now public. It is very unusual for Microsoft not to solve these problems. In a similar incident above, the company took action with a solution within 10 days of the request for defects. The problem is perhaps this time very complex (as we say in the media pop-up) or the company is not likely to work there.
Why there is no explanation from Microsoft still ??