A publisher named ‘Store Ports’ has published the open-source Chromium browser to the Microsoft Store. This is just a UWP wrapper for the desktop browser client. The version of Chromium is version 78, which was released on October 22nd, 2019. With Chrome 84 released in July, this version is an old version without numerous security updates for vulnerabilities. If you wish to use Chromium, you should install the latest version directly from the Chromium Project. This way, you are protected from vulnerabilities that have been fixed since Chrome 78.
Source: https://www.bleepingcomputer.com/news/microsoft/chromium-browser-sneaked-through-review-released-on-microsoft-store/